Name: Author Spotlight: Enhanced Histone PTM Isomer Identification Through LC-TIMS-ToF MS/MS and PASEF
Uploaded: 2024-01-12T12:50:00
Description: Watch this Scientific Journal Video about Histone Modification Screening using Liquid Chromatography, Trapped Ion Mobility Spectrometry, and Time-Of-Flight Mass Spectrometry at JoVE.com

This material is based upon work supported by the National Science Foundation under Grant No. HRD-1547798 and Grant No. HRD-2111661. These NSF Grants were awarded to Florida International University as part of the Centers of Research Excellence in Science and Technology (CREST) Program. This is contribution number 1672 from the Institute of Environment, a Preeminent Program at Florida International University. Additional support was provided by the National Institute of Health under Grant No. R21AI135469 to Francisco Fernandez-Lima and Grant No. R01HD106051 to Benjamin A. Garcia, as well as by the National Science Foundation under Grant No. CHE-2127882 to Benjamin A. Garcia. The authors would like to acknowledge the initial support of Dr. Mario Gomez Hernandez during initial method developments.

NOTE: Histone samples were extracted using a method adapted from Bhanu et al. (2020)12.
1. Sample preparation
<ol>
	<li>Harvesting cultured cells
	<ol>
		<li>When cells are 80% confluent, ensure they are viable using trypan blue exclusion. 
		NOTE: A HeLa S3 cell line was used for these experiments, but this method can be applied to any cultured cells.</li>
		<li>Aspirate the media, then apply 5 mL of 1x phosphate-buffered saline (PBS) to each pl...

Histone Proteomic Analysis and Post-Translational Modification Characterization

<ol>
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Histones are basic proteins that regulate chromatin structure by interacting with DNA in the form of octamers consisting of the four core histones (two each of H2A, H2B, H3, and H4)20. Histones contain numerous lysine and arginine residues, which are readily modified, leading to extensive PTMs that alter the chromatin chemistry by influencing histone function or by binding to other cellular proteins21. PTMs can elicit biological responses by working in tandem, with specific...

In eukaryotic cells, DNA is packaged as chromatin into functional units called nucleosomes. These units are composed of an octamer of four core histones (two each of H2A, H2B, H3, and H4)1,2,3,4. Histones are amongst the most abundant and highly conserved proteins in eukaryotes, which are largely responsible for gene regulation5. Histone posttranslational modifications (PTMs) play a large role in the regulation of chromatin dynamics and rigger various biological processes such as DNA transcription, replication, and repair6. PTMs occur primarily on the accessible surface of the N-terminal regions of histones that are in contact with DNA3,7. However, tail and core modifications influence chromatin structure, altering inter-nucleosome interactions and recruiting specific proteins3,8.
A current challenge during liquid chromatography-mass spectrometry (LC-MS)-based proteomics is the potential co-elution of analytes of interest. In the case of data-dependent analyses (DDA), this translates into the potential loss of several precursor ions during the MS/MS acquisition process9. Time-of-flight (ToF) instruments acquire spectra at very high frequency9,10 (up to tens of kHz)11; this makes them capable of rapidly scanning the total precursor ions within a complex sample (MS1), thus promising optimal sensitivity and MS/MS sequencing rates (up to 100 Hz)9 and making them ideal for biological sample analysis10. Nevertheless, the sensitivity available at these high scan rates is limited by the MS/MS rate9. The addition of trapped ion mobility spectrometry (TIMS) in combination with an orthogonal quadrupole time-of-flight (qToF) mass spectrometer was used to mitigate these limitations. In TIMS, all precursor ions are accumulated in tandem and eluted as a function of their mobility, rather than selecting single precursor masses with a quadrupole9. Parallel accumulation-serial fragmentation (PASEF) allows for hundreds of MS/MS events per second without any loss of sensitivity9.
The principal aim of this work was to show the recent developments of DDA using parallel accumulation in the mobility trap followed by sequential fragmentation and collision-induced dissociation (CID). Histone PTMs were confidently assigned based on their retention times (RTs), mobilities, and fragmentation patterns.

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			<td>Ammonium hydroxide solution, NH4OH</td>
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			<td>Meets ACS Specifications, Meets Reagent Specifications for testing USP/NF monographs GR ACS</td>
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			<td>Thermo Fisher Scientific</td>
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			<td>Bruker Daltonics</td>
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			<td>Bruker Daltonics</td>
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			<td>Bruker Daltonics</td>
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			<td>Bio-Rad</td>
			<td>1610436</td>
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			<td>Deep Well, 96-Well Microplate, 2.0 mL</td>
			<td>Thermo Fisher Scientific</td>
			<td>89237526</td>
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			<td>Disposable Cell Lifters</td>
			<td>Thermo Fisher Scientific</td>
			<td>&#160;08100240</td>
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			<td>Thermo Fisher Scientific</td>
			<td>12-141-363</td>
			<td>Fisherbrand&#160;Pellet Pestles; Resuspend protein and DNA pellets or grind soft tissue in microcentrifuge tubes</td>
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			<td>695076</td>
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			<td>TSP075375</td>
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			<td>A38S</td>
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		<tr>
			<td>Glass Pasteur Pipettes</td>
			<td>Sigma Aldrich</td>
			<td>BR747725-1000EA</td>
			<td></td>
		</tr>
		<tr>
			<td>High-Performance Liquid Chromatograph</td>
			<td>&#160;Shimadzu</td>
			<td></td>
			<td>Shimadzu Prominence 20 HPLC UFLC System</td>
		</tr>
		<tr>
			<td>Hydrochloric acid, HCl</td>
			<td>Sigma Aldrich</td>
			<td>258148</td>
			<td>ACS reagent, 37%</td>
		</tr>
		<tr>
			<td>Hypercarb 30-40 &#956;m Carbon 150&#8211;300 &#197;</td>
			<td>Thermo Fisher Scientific</td>
			<td>60106-402</td>
			<td></td>
		</tr>
		<tr>
			<td>Hypersep cartridge</td>
			<td>Thermo Fisher Scientific</td>
			<td>60109-404</td>
			<td></td>
		</tr>
		<tr>
			<td>LC/MS Calibration Standard, for ESI-ToF</td>
			<td>Agilent</td>
			<td>G1969-85000</td>
			<td>TuningMix</td>
		</tr>
		<tr>
			<td>Magnesium chloride, MgCl2</td>
			<td>Sigma Aldrich</td>
			<td>M8266</td>
			<td>Anhydrous, &#8805;98%</td>
		</tr>
		<tr>
			<td>Methanol, for HPLC</td>
			<td>Thermo Fisher Scientific</td>
			<td>A454</td>
			<td>Optima for HPLC, Fisher Chemical&#160;&#160;</td>
		</tr>
		<tr>
			<td>Microcentrifuge Tube Adapters</td>
			<td>GL Sciences</td>
			<td>501021514</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcystin</td>
			<td>Thermo Fisher Scientific</td>
			<td>50-200-8727</td>
			<td>Enzo Life Sciences&#160;Microcystin-LA</td>
		</tr>
		<tr>
			<td>MS sample vial, LaPhaPack, Snap, 12 mm x 32 mm</td>
			<td>LEAP PAL Parts</td>
			<td>LAP.11190933</td>
			<td></td>
		</tr>
		<tr>
			<td>Nanodrop</td>
			<td>Thermo Fisher Scientific</td>
			<td>model: ND3300</td>
			<td></td>
		</tr>
		<tr>
			<td>Nitrogen (N2)</td>
			<td>Airgas</td>
			<td>NI UHP300</td>
			<td></td>
		</tr>
		<tr>
			<td>PEAKS Studio X+</td>
			<td>Bioinformatic Solutions</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>pH indicator strips, Instachek</td>
			<td>Micro Essential Lab</td>
			<td>JR-113</td>
			<td>Model: Hydrion</td>
		</tr>
		<tr>
			<td>Potassium chloride, KCl</td>
			<td>Sigma Aldrich</td>
			<td>P3911</td>
			<td>ACS reagent, 99.0%&#8211;100.5%</td>
		</tr>
		<tr>
			<td>Pressure Injection Cell</td>
			<td>Next Advance</td>
			<td>&#160;model: PC77</td>
			<td></td>
		</tr>
		<tr>
			<td>Propionic Anhydride</td>
			<td>Sigma Aldrich</td>
			<td>8.00608</td>
			<td>For synthesis</td>
		</tr>
		<tr>
			<td>Refrigerated Centrifuge (700&#8211;18,000 x g)</td>
			<td>NuAire, model: Nuwind</td>
			<td>NU-C200V</td>
			<td></td>
		</tr>
		<tr>
			<td>Reprosil-Pur 120 C18-AQ 3 &#956;m, 3 g</td>
			<td>ESI Source Solutions</td>
			<td>r13.aq.0003</td>
			<td></td>
		</tr>
		<tr>
			<td>SDS-PAGE Gels</td>
			<td>Bio-Rad</td>
			<td>4569035</td>
			<td>Any kD precast polyacrylamide gel, 8.6 cm &#215; 6.7 cm (W &#215; L), for use with Mini-PROTEAN Electrophoresis Cells</td>
		</tr>
		<tr>
			<td>Sodium butyrate</td>
			<td>Thermo Fisher Scientific</td>
			<td>A11079.06</td>
			<td>98+%</td>
		</tr>
		<tr>
			<td>Sodium chloride, NaCl</td>
			<td>Sigma Aldrich</td>
			<td>S9888</td>
			<td>ACS reagent, &#8805;99.0%</td>
		</tr>
		<tr>
			<td>SPE disk, C18</td>
			<td>VWR</td>
			<td>76333-134</td>
			<td>Empore SPE disk, C18, CDS Analytical, 90 mm x 0.5 mm, 12 &#181;m</td>
		</tr>
		<tr>
			<td>SpeedVac+ vacuum pump and plate rotor</td>
			<td>Savant</td>
			<td>model: SC210A</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Millipore</td>
			<td>1.07651</td>
			<td>suitable for microbiology</td>
		</tr>
		<tr>
			<td>Sulfuric acid, H2SO4&#160;</td>
			<td>Sigma Aldrich</td>
			<td>339741</td>
			<td>99.999%</td>
		</tr>
		<tr>
			<td>TIMS-ToF Mass Spectrometer</td>
			<td>Bruker Daltonics</td>
			<td></td>
			<td>model Tims tof ms</td>
		</tr>
		<tr>
			<td>Trichloroacetic acid solution, TCA</td>
			<td>Sigma Aldrich</td>
			<td>T0699</td>
			<td>6.1&#160;N</td>
		</tr>
		<tr>
			<td>Trifluoroacetic acid (TFA)</td>
			<td>Sigma Aldrich</td>
			<td>302031</td>
			<td>Suitable for HPLC, &#8805;99.0%</td>
		</tr>
		<tr>
			<td>Triversa Nanomate</td>
			<td>Advion</td>
			<td>model: TR263</td>
			<td></td>
		</tr>
		<tr>
			<td>TrypsinProtease, MS Grade</td>
			<td>Thermo Fisher Scientific</td>
			<td>90057</td>
			<td></td>
		</tr>
		<tr>
			<td>Tube rotator</td>
			<td>Thermo Fisher Scientific</td>
			<td>88881001</td>
			<td></td>
		</tr>
		<tr>
			<td>Vortex Mixer</td>
			<td>Thermo Fisher Scientific</td>
			<td>88880017</td>
			<td></td>
		</tr>
		<tr>
			<td>Water with 0.1% Formic acid (v/v), LC/MS Grade</td>
			<td>Thermo Fisher Scientific</td>
			<td>LS118</td>
			<td>Optima LC/MS Grade, Thermo Scientific&#160;</td>
		</tr>
	</tbody>
</table>

histone modification screening using liquid chromatography, trapped ion mobility spectrometry, and time-of-flight mass spectrometry

Histone proteins are highly abundant and conserved among eukaryotes and play a large role in gene regulation as a result of structures known as posttranslational modifications (PTMs). Identifying the position and nature of each PTM or pattern of PTMs in reference to external or genetic factors allows this information to be statistically correlated with biological responses such as DNA transcription, replication, or repair. In the present work, a high-throughput analytical protocol for the detection of histone PTMs from biological samples is described. The use of complementary liquid chromatography, trapped ion mobility spectrometry, and time-of-flight mass spectrometry (LC-TIMS-ToF MS/MS) enables the separation and PTM assignment of the most biologically relevant modifications in a single analysis. The described approach takes advantage of recent developments in dependent data acquisition (DDA) using parallel accumulation in the mobility trap, followed by sequential fragmentation and collision-induced dissociation. Histone PTMs are confidently assigned based on their retention time, mobility, and fragmentation pattern.

Histone Modification Screening using Liquid Chromatography, Trapped Ion Mobility Spectrometry, and Time-Of-Flight Mass Spectrometry

A bottom-up proteomic workflow (Figure 7) typically involves the following: extraction of the target protein(s) from a crude sample, followed by quantifying the concentration of the protein(s), and then fractionation, usually by gel electrophoresis or liquid chromatography. After fractionation, the proteins are digested using a proteolytic enzyme (often trypsin), and finally, mass spectrometric analysis of the resulting peptides and protein identification using an established database<sup cl...

Watch this Scientific Journal Video about Histone Modification Screening using Liquid Chromatography, Trapped Ion Mobility Spectrometry, and Time-Of-Flight Mass Spectrometry at JoVE.com

Author Spotlight: Enhanced Histone PTM Isomer Identification Through LC-TIMS-ToF MS/MS and PASEF

An analytical workflow based on liquid chromatography, trapped ion mobility spectrometry, and time-of-flight mass spectrometry (LC-TIMS-ToF MS/MS) for high confidence and highly reproducible "bottom-up" analysis of histone modifications and identification based on principal parameters (retention time [RT], collision cross section [CCS], and accurate mass-to-charge [m/z] ratio).