PUC19N, oligonucleotides המכיל CPD, ו- p44 סופקו בחביבות על ידי סמואל וילסון, Korbinian Heil ותומאס קארל, ואת Gudrun Michels ו Caroline Kisker, בהתאמה. עבודה זו נתמכה על ידי מענקים של דויטשה Forschungsgemeinschaft (DFG) FZ82 ו TE-671/4 ל- IT.

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ניתוח סטטיסטי AFM של עמדות מחייב של חלבונים על שברי דנ&quot;א ארוכים המכילים אתרים ספציפיים היעד יכול לחשוף פרטים מעניינים על אסטרטגיות מסוימות המשמשים את החלבון לזהות אתרים אלה 2 , 3 , 4 , 5 , <sup class=...

מיקרוסקופ כוח אטומי (AFM) הוא טכניקה רבת עוצמה לניתוח אינטראקציות DNA-חלבון 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 . זה דורש רק כמויות נמוכות של חומר המדגם ישירות לדמיין דוגמאות הטרוגניות עם רזולוציה ברמת מולקולה אחת. ההטרוגניות יכולה לנבוע ממצבים קונפורמיים או אוליגומריים שונים של חלבון. בפרט, בהקשר של דגימות DNA חלבון, מתחמי חלבון יכול להציג stoichiometries שונים ו / או קונפורמיות המושרה על ידי DNA מחייב בכלל או מחייב לאתר יעד מסוים בתוך DNA. דגימות הטרוגניות עשויות להכיל גם שני סוגי חלבונים שונים (או יותר), וחלבונים שונים( למשל , המורכבת מסוג אחד בלבד של חלבון לעומת קומפלקסים heteromeric) עשויים לתקשר באופן שונה עם DNA. מחקרים שנדונו כאן לנצל AFM הדמיה באוויר על דגימות סטטי, מיובש של חלבונים לתקן דנ&quot;א כרוך ארוך (~ 900 זוגות, bp) שברי DNA המכילים נגע, המייצג יעד של חלבונים אלה. רזולוציה גבוהה, מולקולרית של AFM מאפשר את ההבחנה בין סוגים שונים של קומפלקסים חלבונים כדי לקבוע את עמדות מחייב של חלבונים על שברי דנ&quot;א. חשוב לציין, נגעים הם הציגו לתוך מצעים דנ&quot;א בעמדות מוגדרים היטב. מכיוון שמיקומו של אתר הנגע בדנ&quot;א ידוע, התפלגות החלבונים הכרוכים בדנ&quot;א מספקת תובנה למאפייני ההזיה השונים (השונים) של מכלולי החלבון (השונים), למשל , עד כמה הם מזהים סוג מסוים של נגע (בהשוואה כדי DNA פגום) 2 , 3 , <supClass = &quot;xref&quot;&gt; 4 , 5 , 6 . עמדותיהם על הדנ&quot;א גם מאפשרות את ההבחנה בין מתחמי חלבון הקשורים ספציפית לנגעים ולמתחמים שאינם קשורים באופן ספציפי למקום אחר בדנ&quot;א. אפיון נפרד של סוגים מורכבים אלה שונים (מתחמים קשורה במיוחד הנגע לעומת קומפלקסים שאינם ספציפיים) יכול לחשוף שינויים קונפורמציה פוטנציאליים במתחמים הנגרמת על זיהוי האתר היעד. חלבונים התיקון DNA התמקדו כאן הם helicases כי הם אחראים להכרה נגע תיקון נוקליאוטיד תיקון כריתה (NER) מסלול. בחיידקים, NER מושגת על ידי חלבונים UvrA, UvrB, ו UvrC. UvrA אחראי על חישה ראשונית של הנגע במכלול UvaA 2 / UvrB 2 . עם אימות הנגע על ידי UvrB זה מורכב ממיר מונומריק UvrB כבול באתר הנגע זה מורכבים ספציפיים יכולים ואז לגייס את pNR. UvrC מכסה טווח קצר (12-13 nt) של DNA בודד תקוע (ssDNA) המכיל את הנגע. החסר החסר הוא מילא לאחר מכן על ידי פולימראז DNA. לבסוף, ה- DNA ligase חותמת את המסור החדש מסונתז עם המקורי DNA 9 , 10 . ב eukaryotes, רוב החלבונים של מפל NER הם חלק גדול, multimeric גורם שעתוק II H (TFIIH) מורכבת. לאחר הנגע הראשונית חישה באמצעות trimeric CEN2-XPC-HR23B מורכבים, TFIIH הוא גויס לאתר היעד DNA. כאשר XPD בתוך המתחם מאמת את נוכחותו של נגע מטרה NER, האנדוקלאס NER האיקריאטי NG ו XPF הם גויסו לבלו קצר (24-32 nt) מתיחה של ssDNA המכיל את הנגע 9 , 10 . כאן, במיוחד, את helicases UvrB ו XPD מ prokaryotic ו eukaryotic NER, בהתאמה, נחקרו. אלה helicases דורשים unaired באזורDNA (בועת דנ&quot;א) על חוט אחד של שני גדילי דנ&quot;א יחיד ולאחר מכן לתרגם לאורך זה גדיל מונעת על ידי הידרוליזה ATP. בנוסף נגעים דנ&quot;א, בועה דנ&quot;א היה ולכן הציג את המצעים המתפקדים כמו טעינת האתר עבור החלבונים. ההליך להכנת מצע DNA ספציפי מצעים תוארה בעבר 11 . זה דורש מבנה דנ&quot;א עגול (פלסמיד) עם שני אתרי הגבלה מקרוב מרווחים עבור nickase. בהקשר של מחקר זה, נעשה שימוש ב- pUC19N (2729 bp) פלסמיד (שנוצר על ידי המעבדה של ס &#39;וילסון, NIEHS). זה פלסמיד מכיל שלושה אתרי הגבלה מקרוב עבור ntase Nbase כי מסגרת 48 נוקלאוטיד (nt) למתוח. לאחר הדגירה עם nickase, את המתיחה של ssDNA בין האתרים האלה ניתן להסיר והוחלף על ידי oligonucleotide המכיל כל תכונה היעד. לאחר כל צעד, עיכול אנזימטי מלא נבדק באמצעות ג&#39;ל agaroseאלקטרופורזה. DNA מעוגל DNA ניתן להבחין בשל הניידות האלקטרופורטית נמוכה יותר לעומת פלסמיד המקורי supercoiled. Gapping של הדנ&quot;א והחלפת מתיחה להסיר על ידי oligonucleotide המצע הספציפיים ניתן להעריך באמצעות עיכול עם אנזים הגבלה אשר חותך את המצע באופן בלעדי באזור בין nicks. לינאריזציה של פלסמיד מעגלי על ידי האנזים ולכן יהיה מדוכא עבור ה- DNA gapped ומשוחזר לאחר החדרת oligonucleotide ספציפיים. לבסוף, שני אתרי הגבלת endonuclease (אידיאלי חותכי יחיד) לאפשר את הדור של מצע דנ&quot;א ליניארי, עם אורך כנדרש ועם אתר היעד הספציפי במיקום מוגדר, כמו גם בועת דנ&quot;א במרחק מן הנגע או 5 &#39;או&#39; 3 &#39;. הכרה של lesions על ידי nlic helicases ניתן לחקור באמצעות הדמיה AFM. טרנספוקציה דנ&quot;א נתקע של helicases ב tהוא אתר lesion גלוי כמו שיא בחלבון הפצה מיקום על הדנ&quot;א ומצביע על זיהוי הנגע. מאחר שהטרנספוקציה של דנ&quot;א של הליקזים אלה היא גם כיוונית, עם קוטביות של 5&#39;עד 3, התלות של זיהוי הנגע על המיקום של אתר הטעינה (בועת ה- DNA במעלה הזרם או במורד הזרם מן הנגע) גם מציינת אם הנגע מוכר באופן מועדף על transocated או על ההפך, לא transocated ssDNA strand 5 , 9 . בסעיפים הבאים, השיטות שיושמו יובאו, וממצאים מרכזיים מניסויים אלה יידונו בקצרה. חשוב לציין, מקביל לעבודה המופתית על תיקון דנ&quot;א המוצג כאן, הדמיה AFM ניתן ליישם את המחקר של מערכות שונות אינטראקציה DNA, כגון שכפול דנ&quot;א או שעתוק 8 , 12 , 13 , 14 </22pl

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Molecular Force Probe (MFP) 3D</td>
			<td>Asylum Research</td>
			<td>N/A</td>
			<td>atomic force microscope (AFM)</td>
		</tr>
		<tr>
			<td>Precision 390</td>
			<td>DELL</td>
			<td>N/A</td>
			<td>computer</td>
		</tr>
		<tr>
			<td>ThermoMixer and 1.5 ml block</td>
			<td>Eppendorf</td>
			<td>5382000015</td>
			<td>heat block for DNA preparation</td>
		</tr>
		<tr>
			<td>Rotilabo Block-Heater H 250 &#38; blocks for 0.5 ml tubes</td>
			<td>Carl Roth GmbH</td>
			<td>Y264.1 &#38; Y267.1</td>
			<td>heat block for protein-DNA incubations</td>
		</tr>
		<tr>
			<td>Mini-Sub Cell GT</td>
			<td>Bio-Rad Laboratories GmbH</td>
			<td>1704467</td>
			<td>electrophoresis chamber with gel caster and power supply</td>
		</tr>
		<tr>
			<td>Power Pac Basic</td>
			<td>Bio-Rad Laboratories GmbH</td>
			<td>1645050</td>
			<td>electrophoresis power supply</td>
		</tr>
		<tr>
			<td>Centifuge 5415 D with rotor</td>
			<td>Eppendorf</td>
			<td>2262120-3</td>
			<td>table centrifuge</td>
		</tr>
		<tr>
			<td>Ultra-Lum electronic UV transillumonator MEB-15</td>
			<td>Ultralum</td>
			<td>900-1322-02</td>
			<td>UV irradiation table</td>
		</tr>
		<tr>
			<td>NanoDrop ND-1000</td>
			<td>VWR International / PEQLAB Biotechnologie GmbH</td>
			<td>N/A</td>
			<td>UV spectrophotometer</td>
		</tr>
		<tr>
			<td>TKAX-CAD with 0.2 &#956;m capsule filter</td>
			<td>Unity Lab Services</td>
			<td>N/A</td>
			<td>water deionization and filter unit</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MFP software on Igor Pro</td>
			<td>Asylum Research</td>
			<td>N/A</td>
			<td>AFM software</td>
		</tr>
		<tr>
			<td>ImageJ (open source Java image processing)</td>
			<td>NIH Image</td>
			<td>N/A</td>
			<td>Image analysis software</td>
		</tr>
		<tr>
			<td>Excel (Microsoft Office)</td>
			<td>Microsoft Corporation</td>
			<td>N/A</td>
			<td>data analysis software</td>
		</tr>
		<tr>
			<td>Origin9 / Origin2016</td>
			<td>OriginLab Corporation</td>
			<td>N/A</td>
			<td>statistical data analysis and graphing software</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Material</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>OMCL-AC240TS</td>
			<td>Olympus</td>
			<td>OMCL-AC240TS</td>
			<td>AFM cantilevers</td>
		</tr>
		<tr>
			<td>grade V-5 muscovite</td>
			<td>SPI Supplies</td>
			<td>1805</td>
			<td>mica sheets</td>
		</tr>
		<tr>
			<td>Amicon Ultra 0.5ml 50k Ultracell</td>
			<td>Millipore Ireland Ltd.</td>
			<td>UFC505096</td>
			<td>centrifuge filters</td>
		</tr>
		<tr>
			<td>NucleoSpin Extract II&#160;</td>
			<td>&#160;Macherey-Nagel GmbH</td>
			<td>740 609.250</td>
			<td>Agarose gel extraction kit</td>
		</tr>
		<tr>
			<td>Rotilabo cellulose paper type 111A</td>
			<td>Carl Roth GmbH</td>
			<td>AP59.1</td>
			<td>AFM deposition blotting paper</td>
		</tr>
		<tr>
			<td>Anatop 25 (0.02 &#956;m)</td>
			<td>Whatman GmbH</td>
			<td>6809-2102</td>
			<td>syringe filter</td>
		</tr>
		<tr>
			<td>SSpI, BspQI</td>
			<td>New England Biolabs (NEB)</td>
			<td>R0132, R0712</td>
			<td>restriction enzymes for DNA substrate preparation</td>
		</tr>
		<tr>
			<td>XhoI, BglII</td>
			<td></td>
			<td>R0146, R0144</td>
			<td>restriction enzymes for DNA preparation controls</td>
		</tr>
		<tr>
			<td>nicking restriction enzyme Nt.BstNBI</td>
			<td>New England Biolabs (NEB)</td>
			<td>R0607</td>
			<td>nickase</td>
		</tr>
		<tr>
			<td>T4 DNA ligase</td>
			<td>New England Biolabs (NEB)</td>
			<td>M0202S</td>
			<td>Ligase</td>
		</tr>
		<tr>
			<td>Tris, HEPES</td>
			<td>Carl Roth GmbH</td>
			<td>4855, 9105</td>
			<td>buffer chemicals</td>
		</tr>
		<tr>
			<td>NaCl, MgCl2, KCl, MgAcetate</td>
			<td>Carl Roth GmbH</td>
			<td>3957, HN03, HN02, P026</td>
			<td>salt chemicals</td>
		</tr>
		<tr>
			<td>NaAc</td>
			<td>Sigma-Aldrich Chemie GmbH</td>
			<td>32318</td>
			<td>salt chemicals</td>
		</tr>
		<tr>
			<td>DTT, TCEP, EDTA</td>
			<td></td>
			<td>6908, HN95, 8040</td>
			<td>chemicals/reagents</td>
		</tr>
		<tr>
			<td>agarose, acetic acid, HCl</td>
			<td>Carl Roth GmbH</td>
			<td>2267, 3738, K025</td>
			<td>reagents</td>
		</tr>
		<tr>
			<td>ATP&#404;S</td>
			<td>Jena Bioscience</td>
			<td>NU-406</td>
			<td>nucleotides</td>
		</tr>
		<tr>
			<td>ATP</td>
			<td>Carl Roth GmbH</td>
			<td>K054</td>
			<td>nucleotides</td>
		</tr>
		<tr>
			<td>oligonucleotide #1 in Table 1</td>
			<td>Biomers</td>
			<td>custom</td>
			<td>complementary DNA oligonucleotide</td>
		</tr>
		<tr>
			<td>oligonucleotides #2, #3, and #6 in Table 1</td>
			<td>Integrated DNA Technologies (IDT)</td>
			<td>custom</td>
			<td>fluorescein containing oligonucleotides</td>
		</tr>
		<tr>
			<td>oligonucleotides #4&#160; and #5 in Table 1</td>
			<td>private (available from e.g. TriLink or GlenResearch)</td>
			<td></td>
			<td>CPD containing oligonucleotides</td>
		</tr>
		<tr>
			<td>SafeSeal reaction tube 0.5 ml and 1.5 ml</td>
			<td>Sarstedt</td>
			<td>72.704 and 72.706</td>
			<td>incubation tubes</td>
		</tr>
		<tr>
			<td>GeneRuler 1 kb</td>
			<td>Thermo Scientific</td>
			<td>SM0311</td>
			<td>DNA ladder</td>
		</tr>
		<tr>
			<td>6x concentrate gel loading dye purple</td>
			<td>New England Biolabs (NEB)</td>
			<td>51406</td>
			<td>DNA loading dye</td>
		</tr>
		<tr>
			<td>Midori Green&#160;</td>
			<td>Nippon Genetics Europe GmbH</td>
			<td>999MG28055</td>
			<td>DNA stain</td>
		</tr>
	</tbody>
</table>

atomic force microscopy investigations of dna lesion recognition in nucleotide excision repair

AFM imaging is a powerful technique for the study of protein-DNA interactions. This single molecule method allows the simultaneous resolution of different molecules and molecular assemblies in a heterogeneous sample. In the particular context of DNA interacting protein systems, different protein complex forms and their corresponding binding positions on target sites containing DNA fragments can thus be distinguished. Here, an application of AFM to the study of DNA lesion recognition in the prokaryotic and eukaryotic nucleotide excision DNA repair (NER) systems is presented. The procedures of DNA and protein sample preparations are described and experimental as well as analytical details of the experiments are provided. The data allow important conclusions on the strategies by which target site verification may be achieved by the NER proteins. Interestingly, they indicate different approaches of lesion recognition and identification for the eukaryotic NER system, depending on the type of lesion. Furthermore, distinct structural properties of the two different helicases involved in prokaryotic and eukaryotic NER result in and explain the different strategies observed for these two systems. Importantly, these experimental and analytical approaches can be applied not only to the study of DNA repair but also very similarly to other DNA interacting protein systems such as those involved in replication or transcription processes.

הבחנה בין סוגים מורכבים שונים המבוססים על כמויות מורכבות של חלבון פעילות helicase של NER helicase prokaryotic UvrB הוא מגורה על ידי DNA מחייב 22 , 23 . UvrB דורש אזור לא מזוהה בדנ&quot;א (בוע...

Watch this Scientific Journal Video about Atomic Force Microscopy Investigations of DNA Lesion Recognition in Nucleotide Excision Repair at JoVE.com

חקירות מיקרוסקופיה של כוח אטומי של זיהוי נגעי DNA בתיקון כריתת נוקלאוטידים | גנטיקה | וִידֵאוֹ

Atomic Force Microscopy Investigations of DNA Lesion Recognition in Nucleotide Excision Repair

Here, the study of different DNA lesion recognition approaches via single molecule AFM imaging is demonstrated with the nucleotide excision repair system as an example. The procedures of DNA and protein sample preparations and experimental as well as analytical details for the AFM experiments are described.

כוח מיקרוסקופי אטומי חקירות של דלקת הנגע הכרה תיקון כריתה נוקליאוטידים

AFM imaging is a powerful technique for the study of protein-DNA interactions. This single molecule method allows the simultaneous resolution of different ...

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9.3K Views.  University of Würzburg. Here, the study of different DNA lesion recognition approaches via single molecule AFM imaging is demonstrated with the nucleotide excision repair system as an example. The procedures of DNA and protein sample preparations and experimental as well as analytical details for the AFM experiments are described.

Video: Atomic Force Microscopy Investigations of DNA Lesion Recognition in Nucleotide Excision Repair

The Visual Colorimetric Detection of Multi-nucleotide Polymorphisms on a Pneumatic Droplet Manipulation Platform

A simple and visual method to detect multi-nucleotide polymorphism (MNP) was performed on a pneumatic droplet manipulation platform on an open surface. This approach to colorimetric DNA detection was based on the hybridization-mediated growth of gold nanoparticle probes (AuNP probes). The growth size and configuration of the AuNP are dominated by the number of DNA samples hybridized with the probes. Based on the specific size- and shape-dependent optical properties of the nanoparticles, the number of mismatches in a sample DNA fragment to the probes is able to be discriminated. The tests were conducted via droplets containing reagents and DNA samples respectively, and were transported and mixed on the pneumatic platform with the controlled pneumatic suction of the flexible PDMS-based superhydrophobic membrane. Droplets can be delivered simultaneously and precisely on an open-surface on the proposed pneumatic platform that is highly biocompatible with no side effect of DNA samples inside the droplets. Combining the two proposed methods, the multi-nucleotide polymorphism can be detected at sight on the pneumatic droplet manipulation platform; no additional instrument is required. The procedure from installing the droplets on the platform to the final result takes less than 5 min, much less than with existing methods. Moreover, this combined MNP detection approach requires a sample volume of only 10 &#181;l in each operation, which is remarkably less than that of a macro system.

This work presents a simple and visual method to detect multi-nucleotide polymorphisms on a pneumatic droplet manipulation platform. With the proposed method, the entire experiment, including droplet manipulation and detection of multi-nucleotide polymorphisms, can be performed near 23 &#176;C without the aid of advanced instruments.

החזותי איתור מדד-צבע של פולימורפיזם רב-נוקלאוטיד על פלטפורמת מניפולציה אגל פניאומטיים

A simple and visual method to detect multi-nucleotide polymorphism (MNP) was performed on a pneumatic droplet manipulation platform on an open surface. ...

In Situ Labeling of Mitochondrial DNA Replication in Drosophila Adult Ovaries by EdU Staining

The mitochondrial genome is inherited exclusively through the maternal line. Understanding of how the mitochondrion and its genome are proliferated and transmitted from one generation to the next through the female oocyte is of fundamental importance. Because of the genetic tractability, and the elegant, ordered simplicity by which oocyte development proceeds, Drosophila oogenesis has become an invaluable system for mitochondrial study. An EdU (5-ethynyl-2&#180;-deoxyuridine) labeling method was utilized to detect mitochondrial DNA (mtDNA) replication in Drosophila ovaries. This method is superior to the BrdU (5-bromo-2'-deoxyuridine) labeling method in that it allows for good structural preservation and efficient fluorescent dye penetration of whole-mount tissues.
Here we describe a detailed protocol for labeling replicating mitochondrial DNA in Drosophila adult ovaries with EdU. Some technical solutions are offered to improve the viability of the ovaries, maintain their health during preparation, and ensure high-quality imaging. Visualization of newly synthesized mtDNA in the ovaries not only reveals the striking temporal and spatial pattern of mtDNA replication through oogenesis, but also allows for simple quantification of mtDNA replication under various genetic and pharmacological perturbations.

In Situ Labeling of Mitochondrial DNA Replication in Drosophila Adult Ovaries by EdU Staining

Drosophila oogenesis continues to be exceptionally useful in the study of mitochondrial proliferation and inheritance. This manuscript describes a detailed protocol used to label the replicating mitochondrial DNA (mtDNA) in Drosophila adult ovaries with 5-ethynyl-2&#180;-deoxyuridine (EdU), which facilitates uncovering mechanisms associated with mitochondrial inheritance that were previously debatable.

באתרו תיוג של דנ&quot;א מיטוכונדריאלי שכפול תסיסנית למבוגרים השחלות ידי edu מכתים

The mitochondrial genome is inherited exclusively through the maternal line. Understanding of how the mitochondrion and its genome are proliferated and ...

Kinetics of Lagging-strand DNA Synthesis In Vitro by the Bacteriophage T7 Replication Proteins

Here we provide protocols for the kinetic examination of lagging-strand DNA synthesis in vitro by the replication proteins of bacteriophage T7. The T7 replisome is one of the simplest replication systems known, composed of only four proteins, which is an attractive feature for biochemical experiments. Special emphasis is placed on the synthesis of ribonucleotide primers by the T7 primase-helicase, which are used by DNA polymerase to initiate DNA synthesis. Because the mechanisms of DNA replication are conserved across evolution, these protocols should be applicable, or useful as a conceptual springboard, to investigators using other model systems. The protocols described here are highly sensitive and an experienced investigator can perform these experiments and obtain data for analysis in about a day. The only specialized piece of equipment required is a rapid-quench flow instrument, but this piece of equipment is relatively common and available from various commercial sources. The major drawbacks of these assays, however, include the use of radioactivity and the relative low throughput.

Kinetics of Lagging-strand DNA Synthesis In Vitro by the Bacteriophage T7 Replication Proteins

We describe sensitive, gel-based discontinuous assays to examine the kinetics of lagging-strand initiation using the replication proteins of bacteriophage T7.

קינטיקה של סינתזת DNA מפגר גדיל<em&gt; במבחנה</em&gt; על ידי חלבונים שכפול bacteriophage T7

Here we provide protocols for the kinetic examination of lagging-strand DNA synthesis in vitro by the replication proteins of bacteriophage T7. The T7 ...

Assessment of DNA Contamination in RNA Samples Based on Ribosomal DNA

One method extensively used for the quantification of gene expression changes and transcript abundances is reverse-transcription quantitative real-time PCR (RT-qPCR). It provides accurate, sensitive, reliable, and reproducible results. Several factors can affect the sensitivity and specificity of RT-qPCR. Residual genomic DNA (gDNA) contaminating RNA samples is one of them. In gene expression analysis, non-specific amplification due to gDNA contamination will overestimate the abundance of transcript levels and can affect the RT-qPCR results. Generally, gDNA is detected by qRT-PCR using primer pairs annealing to intergenic regions or an intron of the gene of interest. Unfortunately, intron/exon annotations are not yet known for all genes from vertebrate, bacteria, protist, fungi, plant, and invertebrate metazoan species.
Here we present a protocol for detection of gDNA contamination in RNA samples by using ribosomal DNA (rDNA)-based primers. The method is based on the unique features of rDNA: their multigene nature, highly conserved sequences, and high frequency in the genome. Also as a case study, a unique set of primers were designed based on the conserved region of ribosomal DNA (rDNA) in the Poaceae family. The universality of these primer pairs was tested by melt curve analysis and agarose gel electrophoresis. Although our method explains how rDNA-based primers can be applied for the gDNA contamination assay in the Poaceae family,&#160;it could be easily used to other prokaryote and eukaryote species

Here, we present a protocol for tracing genomic DNA (gDNA) contamination in RNA samples. The presented method utilizes primers specific for the internal transcribed spacer region (ITS) of ribosomal DNA (rDNA) genes. The method is suited for reliable and sensitive detection of DNA contamination in most eukaryotes and prokaryotes.

הערכה של ה-DNA זיהום בדגימות ה-RNA בהתבסס על Ribosomal DNA

One method extensively used for the quantification of gene expression changes and transcript abundances is reverse-transcription quantitative real-time ...

Genome-wide Mapping of Protein-DNA Interactions with ChEC-seq in Saccharomyces cerevisiae

Genome-wide mapping of protein-DNA interactions is critical for understanding gene regulation, chromatin remodeling, and other chromatin-resident processes. Formaldehyde crosslinking followed by chromatin immunoprecipitation and high-throughput sequencing (X-ChIP-seq) has been used to gain many valuable insights into genome biology. However, X-ChIP-seq has notable limitations linked to crosslinking and sonication. Native ChIP avoids these drawbacks by omitting crosslinking, but often results in poor recovery of chromatin-bound proteins. In addition, all ChIP-based methods are subject to antibody quality considerations. Enzymatic methods for mapping protein-DNA interactions, which involve fusion of a protein of interest to a DNA-modifying enzyme, have also been used to map protein-DNA interactions. We recently combined one such method, chromatin endogenous cleavage (ChEC), with high-throughput sequencing as ChEC-seq. ChEC-seq relies on fusion of a chromatin-associated protein of interest to micrococcal nuclease (MNase) to generate targeted DNA cleavage in the presence of calcium in living cells. ChEC-seq is not based on immunoprecipitation and so circumvents potential concerns with crosslinking, sonication, chromatin solubilization, and antibody quality while providing high resolution mapping with minimal background signal. We envision that ChEC-seq will be a powerful counterpart to ChIP, providing an independent means by which to both validate ChIP-seq findings and discover new insights into genomic regulation.

Genome-wide Mapping of Protein-DNA Interactions with ChEC-seq in Saccharomyces cerevisiae

We describe chromatin endogenous cleavage coupled with high-throughput sequencing (ChEC-seq), a chromatin immunoprecipitation (ChIP)-orthogonal method for mapping protein binding sites genome-wide with micrococcal nuclease (MNase) fusion proteins.

מיפוי רחב של הגנום של אינטראקציות DNA-חלבון עם CHEC-Seq ב<em&gt; Saccharomyces cerevisiae</em

Genome-wide mapping of protein-DNA interactions is critical for understanding gene regulation, chromatin remodeling, and other chromatin-resident ...

Sequence-specific and Selective Recognition of Double-stranded RNAs over Single-stranded RNAs by Chemically Modified Peptide Nucleic Acids

RNAs are emerging as important biomarkers and therapeutic targets. Thus, there is great potential in developing chemical probes and therapeutic ligands for the recognition of RNA sequence and structure. Chemically modified Peptide Nucleic Acid (PNA) oligomers have been recently developed that can recognize RNA duplexes in a sequence-specific manner. PNAs are chemically stable with a neutral peptide-like backbone. PNAs can be synthesized relatively easily by the manual Boc-chemistry solid-phase peptide synthesis method. PNAs are purified by reverse-phase HPLC, followed by molecular weight characterization by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF). Non-denaturing polyacrylamide gel electrophoresis (PAGE) technique facilitates the imaging of the triplex formation, because carefully designed free RNA duplex constructs and PNA bound triplexes often show different migration rates. Non-denaturing PAGE with ethidium bromide post staining is often an easy and informative technique for characterizing the binding affinities and specificities of PNA oligomers. Typically, multiple RNA hairpins or duplexes with single base pair mutations can be used to characterize PNA binding properties, such as binding affinities and specificities. 2-Aminopurine is an isomer of adenine (6-aminopurine); the 2-aminopurine fluorescence intensity is sensitive to local structural environment changes, and is suitable for the monitoring of triplex formation with the 2-aminopurine residue incorporated near the PNA binding site. 2-Aminopurine fluorescence titration can also be used to confirm the binding selectivity of modified PNAs towards targeted double-stranded RNAs (dsRNAs) over single-stranded RNAs (ssRNAs). UV-absorbance-detected thermal melting experiments allow the measurement of the thermal stability of PNA-RNA duplexes and PNA&#183;RNA2 triplexes. Here, we describe the synthesis and purification of PNA oligomers incorporating modified residues, and describe biochemical and biophysical methods for characterization of the recognition of RNA duplexes by the modified PNAs.

We report the protocols for the synthesis and purification of Peptide Nucleic Acid (PNA) oligomers incorporating modified residues. The biochemical and biophysical methods for the characterization of the recognition of RNA duplexes by the modified PNAs are described.

זיהוי רצף ספציפי, סלקטיבי של גדילי כפול RNAs מעל חד גדילי RNAs על ידי שינוי כימי חומצות גרעין פפטיד

RNAs are emerging as important biomarkers and therapeutic targets. Thus, there is great potential in developing chemical probes and therapeutic ligands ...

Profiling DNA Replication Timing Using Zebrafish as an In Vivo Model System

DNA replication timing is an important cellular characteristic, exhibiting significant relationships with chromatin structure, transcription, and DNA mutation rates. Changes in replication timing occur during development and in cancer, but the role replication timing plays in development and disease is not known. Zebrafish were recently established as an in vivo model system to study replication timing. Here is detailed the protocols for using the zebrafish to determine DNA replication timing. After sorting cells from embryos and adult zebrafish, high-resolution genome-wide DNA replication timing patterns can be constructed by determining changes in DNA copy number through analysis of next generation sequencing data. The zebrafish model system allows for evaluation of the replication timing changes that occur in vivo throughout development, and can also be used to assess changes in individual cell types, disease models, or mutant lines. These methods will enable studies investigating the mechanisms and determinants of replication timing establishment and maintenance during development, the role replication timing plays in mutations and tumorigenesis, and the effects of perturbing replication timing on development and disease.

Profiling DNA Replication Timing Using Zebrafish as an In Vivo Model System

Zebrafish were recently used as an in vivo model system to study DNA replication timing during development. Here is detailed the protocols for using zebrafish embryos to profile replication timing. This protocol can be easily adapted to study replication timing in mutants, individual cell types, disease models, and other species.

פרופיל תזמון שכפול ה-DNA באמצעות דג זברה כמערכת מודל In Vivo

DNA replication timing is an important cellular characteristic, exhibiting significant relationships with chromatin structure, transcription, and DNA ...

A Simple, Rapid, and Quantitative Assay to Measure Repair of DNA-protein Crosslinks on Plasmids Transfected into Mammalian Cells

The purpose of this method is to provide a flexible, rapid, and quantitative technique to examine the kinetics of DNA-protein crosslink (DPC) repair in mammalian cell lines. Rather than globally assaying removal of xenobiotic-induced or spontaneous chromosomal DPC removal, this assay examines the repair of a homogeneous, chemically defined lesion specifically introduced at one site within a plasmid DNA substrate. Importantly, this approach avoids the use of radioactive materials and is not dependent on expensive or highly-specialized technology. Instead, it relies on standard recombinant DNA procedures and widely available real-time, quantitative polymerase chain reaction (qPCR) instrumentation. Given the inherent flexibility of the strategy utilized, the size of the crosslinked protein, as well as the nature of the chemical linkage and the precise DNA sequence context of the attachment site can be varied to address the respective contributions of these parameters to the overall efficiency of DPC repair. Using this method, plasmids containing a site-specific DPC were transfected into cells and low molecular weight DNA recovered at various times post-transfection. Recovered DNA is then subjected to strand-specific primer extension (SSPE) using a primer complementary to the damaged strand of the plasmid. Since the DPC lesion blocks Taq DNA polymerase, the ratio of repaired to un-repaired DNA can be quantitatively assessed using qPCR. Cycle threshold (CT) values are used to calculate percent repair at various time points in the respective cell lines. This SSPE-qPCR method can also be used to quantitatively assess the repair kinetics of any DNA adduct that blocks Taq polymerase.

The goal of this protocol is to quantify the repair of defined DNA-protein crosslinks on plasmid DNA. Lesioned plasmids are transfected into recipient mammalian cell lines and low-molecular weight harvested at multiple time points post-transfection. DNA repair kinetics are quantified using strand-specific primer extension followed by qPCR.

הנועד פשוטה, מהירה, כמותית למדוד תיקון של חלבון-דנ א Crosslinks על פלסמידים Transfected בתרבית של תאים

The purpose of this method is to provide a flexible, rapid, and quantitative technique to examine the kinetics of DNA-protein crosslink (DPC) repair in ...

Methodology for Accurate Detection of Mitochondrial DNA Methylation

Quantification of DNA methylation can be achieved using bisulfite sequencing, which takes advantage of the property of sodium bisulfite to convert unmethylated cytosine into uracil, in a single-stranded DNA context. Bisulfite sequencing can be targeted (using PCR) or performed on the whole genome and provides absolute quantification of cytosine methylation at the single base-resolution. Given the distinct nature of nuclear- and mitochondrial DNA, notably in the secondary structure, adaptions of bisulfite sequencing methods for investigating cytosine methylation in mtDNA should be made. Secondary and tertiary structure of mtDNA can indeed lead to bisulfite sequencing artifacts leading to false-positives due to incomplete denaturation poor access of bisulfite to single-stranded DNA. Here, we describe a protocol using an enzymatic digestion of DNA with BamHI coupled with bioinformatic analysis pipeline to allow accurate quantification of cytosine methylation levels in mtDNA. In addition, we provide guidelines for designing the bisulfite sequencing primers specific to mtDNA, in order to avoid targeting undesirable NUclear MiTochondrial segments (NUMTs) inserted into the nuclear genome.

Here, we present a protocol to allow accurate quantification of mitochondrial DNA (mtDNA) methylation. In this protocol, we describe an enzymatic digestion of DNA with BamHI coupled with a bioinformatic analysis pipeline which can be used to avoid overestimation of mtDNA methylation levels caused by the secondary structure of mtDNA.

מתודולוגיה עבור איתור מדויק של מתילציה DNA מיטוכונדריאלי

Quantification of DNA methylation can be achieved using bisulfite sequencing, which takes advantage of the property of sodium bisulfite to convert ...

Use of Frozen Tissue in the Comet Assay for the Evaluation of DNA Damage

The comet assay is gaining popularity as a means to assess DNA damage in cultured cells and tissues, particularly following exposure to chemicals or other environmental stressors. Use of the comet assay in regulatory testing for genotoxic potential in rodents has been driven by adoption of an Organisation for Economic Co-operation and Development (OECD) test guideline in 2014. Comet assay slides are typically prepared from fresh tissue at the time of necropsy; however, freezing tissue samples can avoid logistical challenges associated with simultaneous preparation of slides from multiple organs per animal and from many animals per study. Freezing also enables shipping samples from the exposure facility to a different laboratory for analysis, and storage of frozen tissue facilitates deferring a decision to generate DNA damage data for a given organ. The alkaline comet assay is useful for detecting exposure-related DNA double- and single-strand breaks, alkali-labile lesions, and strand breaks associated with incomplete DNA excision repair. However, DNA damage can also result from mechanical shearing or improper sample processing procedures, confounding the results of the assay. Reproducibility in collection and processing of tissue samples during necropsies may be difficult to control due to fluctuating laboratory personnel with varying levels of experience in harvesting tissues for the comet assay. Enhancing consistency through refresher training or deployment of mobile units staffed with experienced laboratory personnel is costly and may not always be feasible. To optimize consistent generation of high quality samples for comet assay analysis, a method for homogenizing flash frozen cubes of tissue using a customized tissue mincing device was evaluated. Samples prepared for the comet assay by this method compared favorably in quality to fresh and frozen tissue samples prepared by mincing during necropsy. Moreover, low baseline DNA damage was measured in cells from frozen cubes of tissue following prolonged storage.

This protocol describes several procedures for preparing high quality frozen tissue samples at the time of necropsy for use in the comet assay to assess DNA damage: 1) minced tissue, 2) scraped epithelial cells from the gastrointestinal tract, and 3) cubed tissue samples, requiring homogenization using a tissue mincing device.

שימוש ברקמות קפואות בתוך שיטת שביט להערכת נזק לדנ א

The comet assay is gaining popularity as a means to assess DNA damage in cultured cells and tissues, particularly following exposure to chemicals or other ...