Silica-based chromatographic processes for isolating nucleic acid-protein complexes and detecting target nucleic acids
The disclosure relates to methods of detecting a target nucleic acid in a sample using a deactivated RNA-guided nuclease and guide RNA complex. Some methods relate to isolating protein-nucleic acid complexes using silica-based chromatography with certain buffered solutions to better prevent complex dissociation. Some methods relate to isolating protein-nucleic acid complexes using a tagged ribonucleoprotein which binds to a target nucleic acid to form a detectable interconnected network comprising the target nucleic acid. Also provided herein are primer nucleic acids, buffer solutions, and kits for performing the methods of this disclosure for detecting a target nucleic acid in a sample.
1 . A method for detecting a target nucleic acid in a sample, the method comprising:
(a) contacting the sample with
(i) a ribonucleoprotein comprising a deactivated RNA-guided nuclease and a guide RNA (gRNA) configured to bind to the target nucleic acid, wherein the deactivated RNA-guided nuclease comprises a biochemical tag at its N-terminus and C-terminus; and
(ii) a detectable label comprising a plurality of moieties capable of binding to the biochemical tag;
(b) incubating the contacted sample under conditions that promote binding of the detectable label to the biochemical tag and binding of the ribonucleoprotein to the target nucleic acid, whereby an interconnected network of detectable labeled ribonucleoprotein-target nucleic acid complexes is formed;
(c) isolating labeled ribonucleoprotein-target nucleic acid complexes of the interconnected network; and
(d) detecting the detectable label or a target nucleic acid of an isolated ribonucleoprotein-target nucleic acid complex.
2 . The method of claim 1 , wherein the biochemical tag comprises biotin and the detectable label comprise a plurality of streptavidin moieties.
3 . The method of claim 1 , wherein the isolating comprises contacting the interconnected network of detectable labeled ribonucleoprotein-target nucleic acid complexes to a silica or silica-like substrate.
4 . The method of claim 3 , wherein the isolating comprises silica-based chromatographic separating comprising
(a) contacting the interconnected network of detectable labeled ribonucleoprotein-target nucleic acid complexes to a silica or silica-like substrate in the presence of L-arginine or L-lysine;
(b) washing the contacted silica or silica-like substrate using a wash buffer comprising water and one or more of L-arginine, L-lysine, and isopropyl alcohol; and
(c) eluting detectable labeled ribonucleoprotein-target nucleic acid complexes from the washed substrate.
5 . The method of claim 4 , wherein the contacting comprises contacting the interconnected network of detectable labeled ribonucleoprotein-target nucleic acid complexes to a silica or silica-like substrate in the presence of a solution comprising water and one or more of L-arginine, L-lysine, isopropyl alcohol, and ethanol; and optionally wherein the solution comprises between 1.5 and 3 M NaCl, 10 mM ammonium acetate (pH 5.5), and one or more of the following: 1 M L-arginine, 1 M L-lysine, between 5% and 15% isopropyl alcohol, and between 15% and 30% ethanol.
6 . The method of claim 4 , wherein the wash buffer comprises L-arginine or L-lysine and isopropyl alcohol; and optionally wherein the wash buffer comprises 1 M NaCl, 10 mM ammonium acetate (pH 5.5), and one or more of the following: 1 M L-arginine, 1 M L-lysine, and between 5% and 15% isopropyl alcohol.
7 . The method of claim 4 , wherein eluting comprises contacting the washed, contacted substrate to an elution buffer comprising water and one or more of L-arginine, L-lysine, isopropyl alcohol, and a detergent; and optionally wherein the elution buffer comprises NaCl, ammonium acetate, at least 0.5 M L-arginine or at least 0.5 M L-lysine, and between 0.01 and 0.1% polysorbate-20.
8 . The method of claim 1 , further comprising prior to step (a), performing isothermal amplification of target nucleic acids in the sample.
9 . The method of claim 8 , wherein isothermal amplification comprises reverse transcription loop-mediated isothermal amplification (RT-LAMP).
10 . The method of claim 8 , wherein performing isothermal amplification comprises using a primer set selected from:
(a) SEQ ID NOs: 1-6 or six primers having at least 90% or 95% identity thereto;
(b) SEQ ID NOs: 7-11 or five primers having at least 90% or 95% identity thereto;
(c) SEQ ID NOs: 12-17 or six primers having at least 90% or 95% identity thereto;
(d) SEQ ID NOs: 18-22 or five primers having at least 90% or 95% identity thereto;
(e) SEQ ID NOs: 23-28 or six primers having at least 90% or 95% identity thereto;
(f) SEQ ID NOs: 29-34 or six primers having at least 90% or 95% identity thereto;
(g) SEQ ID NOs: 35-39 or five primers having at least 90% or 95% identity thereto;
(h) SEQ ID NOs: 40-43 or four primers having at least 90% or 95% identity thereto;
(i) SEQ ID NOs: 44-49 or six primers having at least 90% or 95% identity thereto; and
(j) SEQ ID NOs: 50-54 or five primers having at least 90% or 95% identity thereto.
11 . The method of claim 1 , wherein the gRNA comprises the nucleic acid of any one of SEQ ID NOs: 56-66.
12 . The method of claim 1 , wherein the detectable label comprises a fluorophore; and optionally wherein the detectable label is part of a quantum dot.
13 . The method of claim 12 , wherein the detectable label comprises a streptavidin-functionalized fluorophore and the biochemical tag comprises biotin; and optionally wherein the detectable label is part of a quantum dot.
14 . The method of claim 1 , wherein the deactivated RNA-guided nuclease is a deactivated Cas9 (dCas9) or deactivated Cas12 (dCas12).
15 . The method of claim 1 , wherein the target nucleic acid is a viral nucleic acid.
16 . The method of claim 15 , wherein the viral nucleic acid is from a virus selected from SARS-2-CoV, Influenza A, and Human Papilloma Virus (HPV).
17 . The method of claim 1 , wherein the sample is a biological sample selected from: blood, saliva, serum, and sputum.