Name: determination of in vitro and cellular turn-on kinetics for fluorogenic rna aptamers
Uploaded: 2022-08-09T14:30:00
Description: Watch this Scientific Journal Video about Determination of In Vitro and Cellular Turn-on Kinetics for Fluorogenic RNA Aptamers at JoVE.com

This work was supported by the following grants to MCH: NSF-BSF 1815508 and NIH R01 GM124589. MRM was partially supported by training grant NIH T32 GM122740.

1. In vitro kinetics experiment
<ol>
	<li>Preparation of DNA templates by PCR
	<ol>
		<li>Set up PCR reaction(s): To prepare PCR reactions, combine the following reagents in a thin-walled PCR tube: 
		33 &#181;L of double-distilled water (ddH2O) 
		10 &#181;L of 5x buffer for high-fidelity DNA polymerase 
		5 &#181;L of 2 mM each deoxyribonucleoside triphosphate (dNTP) 
		0.5 &#181;L of 40 &#181;M forward primer 
		0.5 &#181;L of 40 &#181;M reverse primer<br...

<ol>
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For the in vitro kinetics experiment, the same general protocol can be modified to measure the in vitro kinetics of an RNA-based fluorescent biosensor containing both a ligand-binding and fluorophore-binding domain8. In this case, the RNA should be incubated with the fluorophore prior to measurements upon injecting the ligand in order to obtain ligand response kinetics. If high variability is observed between the replicates, one can troubleshoot by checking that each sample is al...

Fluorogenic reactions are chemical reactions that generate a fluorescence signal. Fluorogenic RNA aptamers typically perform this function by binding a small molecule dye to enhance its fluorescence quantum yield (Figure 1A)1. Different fluorogenic RNA aptamer systems have been developed and consist of specific RNA aptamer sequences and the corresponding dye ligands1. Fluorogenic RNA aptamers have been appended to RNA transcripts as fluorescent tags that enable live cell imaging of mRNAs and non-coding RNAs2,3,4. They have also been placed after promoter sequences as fluorescent reporters of gene expression, similar to the use of green fluorescent protein (GFP) as a reporter, except the reporting function is at the RNA level5,6. Finally, fluorogenic RNA aptamers have been incorporated into RNA-based fluorescent biosensors, which are designed to trigger the fluorogenic reaction in response to a specific small molecule. RNA-based fluorescent biosensors have been developed for live cell imaging of various non-fluorescent metabolites and signaling molecules7,8,9,10,11.
There is growing interest in the development of fluorogenic RNA aptamers to visualize dynamic changes in RNA localization, gene expression, and small molecule signals. For each of these applications, it is desirable to obtain real-time measurements, but the accuracy of the measurements depends on the kinetics of the fluorogenic reaction being faster than the sampling frequency. Here, we describe methods to determine the in vitro kinetics for fluorogenic RNA aptamers Spinach212&#160;and Broccoli13 using a plate reader equipped with a sample injector and to determine the cellular turn-on kinetics for Spinach2 expressed in Escherichia coli using a flow cytometer. These two RNA aptamers were chosen because they have been applied to study RNA localization2,3,4, they have been used in reporters5, 6 and biosensors7,8,9,10,11, and the corresponding dye ligands (DFHBI or DFHBI-1T) are commercially available. A summary of their in vitro properties determined in the literature is given in Table 14,13,14, which informed the protocol development (e.g., the wavelengths and dye concentrations used). These results demonstrate that the fluorogenic reactions affected by RNA aptamers are rapid and should not impede accurate measurements for the desired cell biological applications.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Agarose</td>
			<td>Thermo Fischer Scientific</td>
			<td>BP160500</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose gel electrophoresis equipment</td>
			<td>Thermo Fischer Scientific</td>
			<td>B1A-BP</td>
			<td></td>
		</tr>
		<tr>
			<td>Alpha D-(+)-lactose monohydrate</td>
			<td>Thermo Fischer Scientific</td>
			<td>18-600-440</td>
			<td></td>
		</tr>
		<tr>
			<td>Amber 1.5 mL microcentrifuge tubes</td>
			<td>Thermo Fischer Scientific</td>
			<td>22431021</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium persulfate (APS)</td>
			<td>Sigma-Aldrich</td>
			<td>A3678</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium sulfate ((NH4)2SO4)</td>
			<td>Sigma-Aldrich</td>
			<td>A4418</td>
			<td></td>
		</tr>
		<tr>
			<td>Attune NxT Flow cytometer</td>
			<td>Thermo Fischer Scientific</td>
			<td>A24861</td>
			<td></td>
		</tr>
		<tr>
			<td>Attune 1x Focusing Fluid</td>
			<td>Thermo Fischer Scientific</td>
			<td>A24904</td>
			<td></td>
		</tr>
		<tr>
			<td>Attune Shutdown Solution</td>
			<td>Thermo Fischer Scientific</td>
			<td>A24975</td>
			<td></td>
		</tr>
		<tr>
			<td>Attune Performance Tracking Beads</td>
			<td>Thermo Fischer Scientific</td>
			<td>4449754</td>
			<td></td>
		</tr>
		<tr>
			<td>Attune Wash Solution</td>
			<td>Thermo Fischer Scientific</td>
			<td>&#160;J24974</td>
			<td></td>
		</tr>
		<tr>
			<td>Boric acid</td>
			<td>Sigma-Aldrich</td>
			<td>B6768</td>
			<td></td>
		</tr>
		<tr>
			<td>Bromophenol blue</td>
			<td>Sigma-Aldrich</td>
			<td>B0126</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbenicillin disodium salt</td>
			<td>Sigma-Aldrich</td>
			<td>C3416</td>
			<td></td>
		</tr>
		<tr>
			<td>Chlorine Bleach</td>
			<td>Amazon</td>
			<td>B07J6FJR8D</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning Costar 96-well plate</td>
			<td>Daigger Scientific</td>
			<td>EF86610A</td>
			<td></td>
		</tr>
		<tr>
			<td>Culture Tubes, 12 mm x 75 mm, 5 mL with attached dual position cap</td>
			<td>Globe Scientific</td>
			<td>05-402-31</td>
			<td></td>
		</tr>
		<tr>
			<td>DFHBI</td>
			<td>Sigma-Aldrich</td>
			<td>SML1627</td>
			<td></td>
		</tr>
		<tr>
			<td>DFHBI-1T</td>
			<td>Sigma-Aldrich</td>
			<td>SML2697</td>
			<td></td>
		</tr>
		<tr>
			<td>D-Glucose (anhydrous)</td>
			<td>Acros Organics</td>
			<td>AC410955000</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide (DMSO)</td>
			<td>Sigma-Aldrich</td>
			<td>D8418</td>
			<td></td>
		</tr>
		<tr>
			<td>Dithiothreitol (DTT)</td>
			<td>Sigma-Aldrich</td>
			<td>DTT-RO</td>
			<td></td>
		</tr>
		<tr>
			<td>DNA loading dye</td>
			<td>New England Biolabs</td>
			<td>B7025S</td>
			<td></td>
		</tr>
		<tr>
			<td>DNA LoBind Tubes (2.0 mL)</td>
			<td>Eppendorf</td>
			<td>22431048</td>
			<td></td>
		</tr>
		<tr>
			<td>dNTPs: dATP, dCTP, dGTP, dTTP</td>
			<td>New England Biolabs</td>
			<td>N0446S</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA, pH 8.0</td>
			<td>Gibco, Life Technologies</td>
			<td>AM9260G</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol (EtOH)</td>
			<td>Sigma-Aldrich</td>
			<td>E7023</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter-tip micropipettor tips</td>
			<td>Thermo Fischer Scientific</td>
			<td>AM12635, AM12648, AM12655, AM12665</td>
			<td></td>
		</tr>
		<tr>
			<td>FlowJo Software</td>
			<td>BD Biosciences</td>
			<td>N/A</td>
			<td>FlowJo v10 Software</td>
		</tr>
		<tr>
			<td>Fluorescent plate reader with heating control</td>
			<td>VWR</td>
			<td>10014-924</td>
			<td></td>
		</tr>
		<tr>
			<td>Gel electrophoresis power supply</td>
			<td>Thermo Fischer Scientific</td>
			<td>EC3000XL2</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Sigma-Aldrich</td>
			<td>G5516</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycogen AM95010</td>
			<td>Thermo Fischer Scientific</td>
			<td>AM95010</td>
			<td></td>
		</tr>
		<tr>
			<td>GraphPad Prism</td>
			<td>Dotmatics</td>
			<td>N/A</td>
			<td>Analysis software from Academic Group License&#160;</td>
		</tr>
		<tr>
			<td>Heat block&#160;</td>
			<td>Thomas Scientific</td>
			<td>1159Z11</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma-Aldrich</td>
			<td>H-4034</td>
			<td></td>
		</tr>
		<tr>
			<td>Inorganic pyrophosphatase</td>
			<td>Sigma-Aldrich</td>
			<td>I1643-500UN</td>
			<td></td>
		</tr>
		<tr>
			<td>Low Molecular Weight DNA Ladder</td>
			<td>New England Biolabs</td>
			<td>N3233L</td>
			<td>Supplied with free vial of Gel Loading Dye, Purple (6x), no SDS (NEB #B7025).</td>
		</tr>
		<tr>
			<td>Magnesium chloride hexahydrate (MgCl2)</td>
			<td>Sigma-Aldrich</td>
			<td>M2670</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium sulfate (MgSO4)</td>
			<td>Fisher Scientific</td>
			<td>MFCD00011110</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcentrifuge tubes (1.5 mL)</td>
			<td>Eppendorf</td>
			<td>22363204</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcentrifuge with temperature control</td>
			<td>Marshall Scientific</td>
			<td>EP-5415R</td>
			<td></td>
		</tr>
		<tr>
			<td>Micropipettors</td>
			<td>Gilson</td>
			<td>FA10001M, FA10003M, FA10005M, FA10006M</td>
			<td></td>
		</tr>
		<tr>
			<td>Micropipettor tips</td>
			<td>Sigma-Aldrich</td>
			<td>Z369004, AXYT200CR, AXYT1000CR</td>
			<td></td>
		</tr>
		<tr>
			<td>Millipore water filter with BioPak unit</td>
			<td>Sigma-Aldrich</td>
			<td>CDUFBI001, ZRQSVR3WW</td>
			<td></td>
		</tr>
		<tr>
			<td>Narrow micropipettor pipette tips</td>
			<td>DOT Scientific</td>
			<td>RN005R-LRS</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS, 10x</td>
			<td>Thermo Fischer Scientific</td>
			<td>BP39920</td>
			<td></td>
		</tr>
		<tr>
			<td>PCR clean-up kit</td>
			<td>Qiagen</td>
			<td>28181</td>
			<td></td>
		</tr>
		<tr>
			<td>PCR primers and templates</td>
			<td>Integrated DNA technologies</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PCR thermocycler for thin-walled PCR tubes</td>
			<td>Bio-Rad</td>
			<td>1851148</td>
			<td></td>
		</tr>
		<tr>
			<td>PCR thermocycler for 0.5 mL tubes</td>
			<td>Techne</td>
			<td>5PRIME/C</td>
			<td></td>
		</tr>
		<tr>
			<td>pET31b-T7-Spinach2 Plasmid</td>
			<td>Addgene</td>
			<td>Plasmid #79783</td>
			<td></td>
		</tr>
		<tr>
			<td>Phusion High-Fidelity DNA polymerase&#160;</td>
			<td>New England Biolabs</td>
			<td>M0530L</td>
			<td>Purchase of Phusion High-Fideldity Enzyme is supplied with 5x Phusion HF Buffer, 5x Phusion GC Buffer, and MgCl2 and DMSO solutions.</td>
		</tr>
		<tr>
			<td>Polyacrylamide gel electrophoresis gel comb, C.B.S. Scientific</td>
			<td>C.B.S. Scientific</td>
			<td>VGC-1508</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyacrylamide gel electrophoresis equipment</td>
			<td>C.B.S. Scientific</td>
			<td>ASG-250</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium chloride (KCl)</td>
			<td>Sigma-Aldrich</td>
			<td>P9333</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium phosphate monobasic</td>
			<td>Sigma-Aldrich</td>
			<td>P5655</td>
			<td></td>
		</tr>
		<tr>
			<td>Razor blades</td>
			<td>Genesee Scientific</td>
			<td>38-101</td>
			<td></td>
		</tr>
		<tr>
			<td>rNTPs: ATP, CTP, GTP, UTP</td>
			<td>New England Biolabs</td>
			<td>N0450L</td>
			<td></td>
		</tr>
		<tr>
			<td>SDS</td>
			<td>Sigma-Aldrich</td>
			<td>L3771</td>
			<td></td>
		</tr>
		<tr>
			<td>Short wave UV light source</td>
			<td>Thermo Fischer Scientific</td>
			<td>11758221</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium carbonate (Na2CO3)</td>
			<td>Sigma-Aldrich</td>
			<td>S7795</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride (NaCl)</td>
			<td>Sigma-Aldrich</td>
			<td>S7653</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide (NaOH)</td>
			<td>Sigma-Aldrich</td>
			<td>S8045</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium phosphate dibasic, anhydrous</td>
			<td>Thermo Fischer Scientific</td>
			<td>S375-500</td>
			<td></td>
		</tr>
		<tr>
			<td>SoftMax Pro</td>
			<td>Molecular Devices</td>
			<td>N/A</td>
			<td>SoftMax Pro 6.5.1 (platereader software) obtained through Academic Group License</td>
		</tr>
		<tr>
			<td>Sterile filter units</td>
			<td>Thermo Fischer Scientific</td>
			<td>09-741-88</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Sigma-Aldrich</td>
			<td>S0389</td>
			<td></td>
		</tr>
		<tr>
			<td>SYBR Safe DNA gel stain</td>
			<td>Thermo Fischer Scientific</td>
			<td>S33102</td>
			<td></td>
		</tr>
		<tr>
			<td>TAE buffer for agarose gel electrophoresis</td>
			<td>Thermo Fischer Scientific</td>
			<td>AM9869</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetramethylethylenediamine (TEMED)</td>
			<td>Sigma-Aldrich</td>
			<td>T9281</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris base</td>
			<td>Sigma-Aldrich</td>
			<td>TRIS-RO</td>
			<td></td>
		</tr>
		<tr>
			<td>Tryptone (granulated)</td>
			<td>Thermo Fischer Scientific</td>
			<td>M0251S</td>
			<td></td>
		</tr>
		<tr>
			<td>T7 RNA polymerase</td>
			<td>New England Biolabs</td>
			<td>M0251S</td>
			<td></td>
		</tr>
		<tr>
			<td>Urea-PAGE Gel system&#160;</td>
			<td>National Diagnostics</td>
			<td>EC-833</td>
			<td></td>
		</tr>
		<tr>
			<td>UV fluorescent TLC plate</td>
			<td>Sigma-Aldrich</td>
			<td>1.05789.0001</td>
			<td></td>
		</tr>
		<tr>
			<td>UV/Vis spectrophotometer</td>
			<td>Thermo Fischer Scientific</td>
			<td>ND-8000-GL</td>
			<td></td>
		</tr>
		<tr>
			<td>Vortex mixer</td>
			<td>Thermo Fischer Scientific</td>
			<td>2215415</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylene cyanol</td>
			<td>Sigma-Aldrich</td>
			<td>X4126</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast Extract (Granulated)</td>
			<td>Thermo Fischer Scientific</td>
			<td>BP9727-2</td>
			<td></td>
		</tr>
	</tbody>
</table>

determination of in vitro and cellular turn-on kinetics for fluorogenic rna aptamers

Fluorogenic RNA aptamers have been applied in live cells to tag and visualize RNAs, report on gene expression, and activate fluorescent biosensors that detect levels of metabolites and signaling molecules. In order to study dynamic changes in each of these systems, it is desirable to obtain real-time measurements, but the accuracy of the measurements depends on the kinetics of the fluorogenic reaction being faster than the sampling frequency. Here, we describe methods to determine the in vitro and cellular turn-on kinetics for fluorogenic RNA aptamers using a plate reader equipped with a sample injector and a flow cytometer, respectively. We show that the in vitro kinetics for the fluorescence activation of the Spinach2 and Broccoli aptamers can be modeled as two-phase association reactions and have differing fast phase rate constants of 0.56 s&#8722;1 and 0.35 s&#8722;1, respectively. In addition, we show that the cellular kinetics for the fluorescence activation of Spinach2 in Escherichia coli, which is further limited by dye diffusion into the Gram-negative bacteria, is still sufficiently rapid to enable accurate sampling frequency on the minute timescale. These methods to analyze fluorescence activation kinetics are applicable to other fluorogenic RNA aptamers that have been developed.

In vitro kinetics 
The sequences of the DNA templates and primers, which are purchased as synthetic oligonucleotides, are shown in Table 2, and the reagent recipes are shown in Supplementary File 1. PCR amplification is used to scale up the amount of DNA template with the T7 promoter, which is required for the subsequent in vitro transcription (IVT) reaction. In addition, PCR amplification can be used for two purposes in the same r...

Watch this Scientific Journal Video about Determination of In Vitro and Cellular Turn-on Kinetics for Fluorogenic RNA Aptamers at JoVE.com

Determination of In Vitro and Cellular Turn-on Kinetics for Fluorogenic RNA Aptamers

The protocol presents two methods to determine the kinetics of the fluorogenic RNA aptamers Spinach2 and Broccoli. The first method describes how to measure fluorogenic aptamer kinetics in vitro with a plate reader, while the second method details the measurement of fluorogenic aptamer kinetics in cells by flow cytometry.

Determination of In Vitro and Cellular Turn-on Kinetics for Fluorogenic RNA Aptamers

Fluorogenic RNA aptamers have been applied in live cells to tag and visualize RNAs, report on gene expression, and activate fluorescent biosensors that ...

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