Double-stranded conformational polymorphism analysis

Abstract

Double-stranded conformational polymorphism analysis is performed by combining a probe comprising a cross-linking agent and optionally a label with a sample having a target sequence, which may be complementary or have one or a few mismatches with respect to the probe sequence. After sufficient time for hybridization under mild or lesser stringency conditions, hybridized pairs are irradiated to induce cross-link formation by the cross-linking agent. The sample is then analyzed by denaturing gel electrophoresis where the rate of migration depends upon the degree of complementarity between the probe and the target. For corroboration, in a second experiment, the probe may be combined with the sample under high stringency conditions, where it is found that the formation of cross-linked probe/target is substantially lower for pairs having mismatches than for fully matched pairs. After cross-linking, the sample may be separated by gel electrophoresis, and the amount of cross-linked nucleic acid determined.

What is claimed is:  
     
         1 . A method of detecting the presence or absence of at least one mismatch between a nucleic acid probe and a nucleic acid target, wherein said probe and target have sequences which differ by not more than five mismatches, said probe comprising a known sequence and a photoactivatable cross-linking agent, which when said probe sequence is hybridized to said target sequence, upon photoactivation forms a covalent bond between said probe sequence and said target sequence, said method comprising: 
 combining, in a hybridizing medium, a nucleic acid sample comprising said target and said probe under mild stringency hybridizing conditions for a time sufficient for said target and said probe to hybridize;    irradiating said hybridizing medium to form cross-links between said probe and target sequence to which said probe is hybridized to from cross-linked double-stranded nucleic acid;    separating nucleic acid in said hybridizing medium by denaturing electrophoresis and comparing the migratory rate of said cross-linked double-stranded nucleic acid to a known mismatched or matched cross-linked double-stranded nucleic acid standard, whereby the presence or absence of said at least one mismatch is determined.    
     
     
         2 . A method according to    claim 1   , wherein said probe is labeled with a detectable label.  
     
     
         3 . A method according to    claim 1   , wherein said sample is prepared using the polymerase chain reaction and said sample nucleic acid is labeled with a detectable label.  
     
     
         4 . A method according to    claim 1   , wherein said electrophoresis is polyacrylamide gel electrophoresis.  
     
     
         5 . A method of detecting the presence or absence of at least one mismatch between a nucleic acid probe and a nucleic acid target, wherein said probe and target have sequences which differ by not more than five mismatches, said target sequence comprising a nucleic acid molecule of from about 25 to 300 nt and said probe comprising a known sequence of from 15 to 50 nt and a photoactivatable cross-linking agent, which when said probe sequence is hybridized to said target sequence, upon photoactivation forms a covalent bond between said probe sequence and said target sequence, said method comprising: 
 combining, in a hybridizing medium, a nucleic acid sample comprising said target and said probe under mild stringency hybridizing conditions for a time sufficient for said target and said probe to hybridize;    irradiating at a wavelength in the range of about 300-400 nm said hybridizing medium to form cross-links between said probe and target sequence to which said probe is hybridized to cross-linked double-stranded nucleic acid;    separating nucleic acid in said hybridizing medium by denaturing electrophoresis and comparing the migratory rate of said cross-linked double-stranded nucleic acid to a known mismatched or matched cross-linked double-stranded nucleic acid standard, whereby the presence or absence of said at least one mismatch is determined.    
     
     
         6 . A method according to    claim 5   , wherein said sample is prepared by restriction enzyme digestion of genomic DNA.  
     
     
         7 . A method according to    claim 5   , wherein said sample is prepared using the polymerase chain reaction and said sample nucleic acid is labeled with a detectable label.  
     
     
         8 . A method according to    claim 5   , wherein said probe is labeled with a detectable label.  
     
     
         9 . A method according to    claim 5   , wherein said electrophoresis is polyacrylamide gel electrophoresis.  
     
     
         10 . A method of detecting the presence or absence of at least one mismatch between a nucleic acid probe and a nucleic acid target, wherein said probe and target have sequences which differ by not more than five mismatches, said target sequence comprising a nucleic acid molecule of from about 25 to 300 nt and said probe comprising a known sequence of from 15 to 50 nt and a photoactivatable cross-linking agent, which when said probe sequence is hybridized to said target sequence, upon photoactivation forms a covalent bond between said probe sequence and said target sequence, said method comprising: 
 combining, in a hybridizing medium, a nucleic acid sample comprising said target and said probe under mild stringency hybridizing conditions equivalent to a temperature in the range of 25-70° C. and with 0.1-1.5 M sodium for a time sufficient for said target and said probe to hybridize;    irradiating at a wavelength in the range of about 300-400 nm said hybridizing medium to form cross-links between said probe and target sequence to which said probe is hybridized to from cross-linked double-stranded nucleic acid;    separating nucleic acid in said hybridizing medium by denaturing gel electrophoresis and comparing the migratory rate of said cross-linked double-stranded nucleic acid to a known mismatched or matched cross-linked double-stranded nucleic acid standard, whereby the presence or absence of said at least one mismatch is determined.    
     
     
         11 . A method according to    claim 10   , wherein said cross-linking agent comprises a coumarinyl group.  
     
     
         12 . A method of detecting the presence or absence of at least one mismatch between a nucleic acid probe and a nucleic acid target, wherein said probe and target have sequences which differ by not more than five mismatches, said target sequence comprising a nucleic acid molecule of from about 25 to 300 nt and said probe comprising a known sequence of from 15 to 50 nt and a photoactivatable cross-linking agent, which when said probe sequence is hybridized to said target sequence, upon photoactivation forms a covalent bond between said probe sequence and said target sequence, said method comprising: 
 combining, in a hybridizing medium, a nucleic acid sample comprising said target and said probe under high stringency hybridizing conditions for a time sufficient for said target and said probe to hybridize, where a probe complementary to said target results in at least about a 2-fold greater amount of hybridization than a mismatched probe;    irradiating at a wavelength in the range of about 300-400 nm said hybridizing medium to form cross-links between said probe and target sequence to which said probe is hybridized to cross-linked double-stranded nucleic acid;    separating nucleic acid in said hybridizing medium by denaturing electrophoresis and determining the amount of cross-linked double-stranded nucleic acid, where the amount of cross-linked double-stranded nucleic acid is related to the presence or absence of mismatches between said probe and said target.    
     
     
         13 . A method according to    claim 12   , wherein said high stringency conditions are at least equivalent to a temperature in the range of about 40-70° C. and 0.05 to 0.5 M sodium ion.  
     
     
         14 . A kit comprising two probes, characterized by consisting of from 15 to 50 nt, joined to each of said probes is a photoactivatable cross-linking agent, each of said probes differing with the other probe by not more than 3 mismatches, and being naturally occurring sequences.  
     
     
         15 . A kit according to    claim 14   , wherein said photoactivatable cross-linking agent comprises a coumarinyl group.  
     
     
         16 . A kit according to    claim 14   , wherein said naturally occurring sequences are related by one being the mutant of the other.  
     
     
         17 . A kit according to    claim 14   , wherein said naturally occurring sequences are related by one being the allele of the other.  
     
     
         18 . A kit according to    claim 14   , wherein said probes are labeled with a detectable label.  
     
     
         19 . A kit according to    claim 14   , wherein each of said probes has a plurality of cross-linking agents.