Probe for nucleic acid sequencing and methods of use

Abstract

A nanoprobe for sequencing of nucleic acid molecules is provided, as well as methods for using the nanoprobe. In particular examples, the probe includes a polymerizing agent and one or more molecular linkers that carry a chemical moiety capable of reversibly binding to the template strand of a nucleic acid molecule, without being detached from the linker, by specifically binding with a complementary nucleotide in the target nucleic acid molecule. The reversible binding of the chemical moiety on the linker with a complementary nucleotide in the target nucleic acid molecule is indicated by emission of a characteristic signal that indicates pairing of the chemical moiety on the linker with its complementary nucleotide. An example of such a chemical moiety is a nonhydrolyzable nucleotide analog. In particular examples, the polymerizing agent and the chemical moiety are associated with a tag, such as a donor fluorophore and acceptor fluorophore characteristic of the particular type of chemical moiety.

1 . A probe for sequencing a nucleic acid molecule, comprising:
 a polymerizing agent having an active site capable of binding to a target nucleic acid molecule and promoting synthesis of a complementary nucleic acid molecule that elongates as complementary nucleotides are incorporated into the complementary nucleic acid molecule; and   one or more molecular linkers spaced apart on the polymerizing agent,
 wherein the molecular linkers are attached to the polymerizing agent via a tether; 
 wherein the molecular linkers form a symmetrical branch structure, and 
 wherein each branch carries a different nucleotide analog that is capable of reversibly binding to the target nucleic acid molecule, without being detached from the linker, by specifically binding with a complementary nucleotide in the target nucleic acid molecule, wherein specific binding of the nucleotide analog on the linker with a complementary nucleotide in the target nucleic acid molecule is indicated by emission of a characteristic signal that indicates pairing of the nucleotide analog on the linker with its complementary nucleotide. 
   
     
     
         2 . The probe of  claim 1 , wherein the nucleotide analog comprises a non-hydrolyzable nucleotide analog. 
     
     
         3 . The probe of  claim 2 , wherein the non-hydrolyzable nucleotide analog comprises a non-hydrolyzable triphosphate nucleotide analog. 
     
     
         4 . The probe of  claim 1 , where the nucleotide analog is a mono-nucleotide. 
     
     
         5 . The probe of  claim 1 , wherein the branch structure comprises at least four branches, wherein each branch carries a different nucleotide analog capable of specifically binding with a different nucleotide in the target nucleic acid molecule. 
     
     
         6 . The probe of  claim 1 , wherein the polymerizing agent is associated with a tag, and wherein each of the nucleotide analogs is associated with a tag that identifies a particular nucleotide analog carried by the linker, wherein interaction of the tag associated with the polymerizing agent with the tag associated with the nucleotide analog induces emission of the characteristic signal that indicates pairing of the nucleotide analog on the linker with its complementary nucleotide in the target nucleic acid molecule. 
     
     
         7 . The probe of  claim 6 , wherein the tag associated with the polymerizing agent forms a donor-acceptor pair with the tag associated with each nucleotide analog, whereby interaction of the donor-acceptor pair stimulates emission of the characteristic signal. 
     
     
         8 . The probe of  claim 7 , wherein the donor-acceptor pair comprise a donor that is stimulated by application of an external stimulus to emit a stimulus to which the acceptor reacts to emit the characteristic signal. 
     
     
         9 . The probe of  claim 6 , wherein each tag comprises a fluorophore. 
     
     
         10 . The probe of  claim 6 , wherein each of the tags that identifies a particular nucleotide analog carried by the linker, comprises one or more fluorophores that emits a unique emission signal. 
     
     
         11 . The probe of  claim 1 , wherein the molecular linkers comprise linear polymers. 
     
     
         12 . The probe of  claim 11 , wherein the polymers comprise nucleic acids. 
     
     
         13 . The probe of  claim 1 , wherein the one or more molecular linkers maintain the polymerizing agent and the nucleotide analog sufficiently spaced a distance from one another to avoid substantial entanglement of the polymerizing agent and the nucleotide analog in an absence of the target nucleic acid molecule. 
     
     
         14 . The probe of  claim 1 , wherein at least a portion of the molecular linker is of a sufficient rigidity to reduce interaction of the polymerizing agent and the nucleotide analog in the absence of the target nucleic acid molecule. 
     
     
         15 . The probe of  claim 1 , wherein the molecular linker comprises a tether, a molecular rod, or combinations thereof. 
     
     
         16 . The probe of  claim 15 , wherein the molecular rod comprises a double-stranded DNA (dsDNA) of at least 10 nucleotides. 
     
     
         17 . The probe of  claim 15 , wherein the tether comprises polyethylene glycol (PEG). 
     
     
         18 . The probe of  claim 1  where the polymerizing agent comprises a DNA polymerase, RNA polymerase, ribosome, or reverse transcriptase. 
     
     
         19 . The probe of  claim 1 , further comprising a primer that specifically hybridizes to the target nucleic acid sequence under high stringency conditions, wherein the primer is attached to the polymerizing agent via a molecular linker. 
     
     
         20 . The probe of  claim 6 , wherein the tags associated with the nucleotide analogs are a coded fluorophore set that permits the detection and correction of errors. 
     
     
         21 . A method of determining a nucleic acid sequence of a target nucleic acid molecule, comprising:
 exposing the target nucleic acid molecule to the probe of  claim 1  in the presence of an oligonucleotide primer and a mixture of hydrolyzable nucleotides that are capable of being incorporated into an elongating nucleic acid molecule by hybridizing with a complementary nucleotide in the target nucleic acid molecule, and replacing the nucleotide analog that reversibly binds to the template nucleic acid molecule;   detecting emission of a sequence of signals comprising emission of a plurality of the characteristic signals that indicates pairing of the nucleotide analog on the molecular linker with its complementary nucleotide.   
     
     
         22 . The method of  claim 21 , wherein the polymerizing agent is associated with a tag, and each of the nucleotide analogs is also associated with a tag that identifies a particular nucleotide analog carried by the linker, wherein interaction of the tag associated with the polymerizing agent with the tag associated with the nucleotide analogs induces emission of the characteristic signal that indicates pairing of the nucleotide analogs on the linker with its complementary nucleotide. 
     
     
         23 . The method of  claim 22 , wherein the tag associated with the polymerizing agent comprises a donor fluorophore and the tag that identifies a particular nucleotide analog comprises one or more acceptor fluorophores, wherein interaction of the polymerizing agent and the nucleotide analog that specifically binds to the complementary nucleotide in the target nucleic acid molecule brings the acceptor fluorophore into a proximity with a donor fluorophore to permit excitation of the acceptor fluorophore by the donor fluorophore. 
     
     
         24 . The method of  claim 23 , wherein detecting the signal comprises detecting a fluorescent signal emitted from the acceptor fluorophore or comprises detecting a reduction in fluorescent signal emitted from the donor fluorophore. 
     
     
         25 . The method of  claim 21 , wherein the emission of a sequence of signals is converted into a nucleic acid sequence. 
     
     
         26 . The method of  claim 21 , wherein the emission of a sequence of signals is generated by luminescence resonance energy transfer (LRET) or Förster resonance energy transfer (FRET). 
     
     
         27 . The method of  claim 26 , further comprising exciting the donor fluorophore to emit a signal which excites the one or more acceptor fluorophores to emit the characteristic signal that indicates pairing of the nucleotide analog on the linker with its complementary nucleotide. 
     
     
         28 . The method of  claim 21 , wherein the polymerizing agent is a GFP-polymerase. 
     
     
         29 . The method of  claim 21 , wherein the probe is fixed to a substrate. 
     
     
         30 . The method of  claim 29 , wherein the polymerizing agent is fixed to the substrate by a linker. 
     
     
         31 . The method of  claim 21 , wherein the target nucleic acid molecule or the oligonucleotide primer is fixed to a substrate. 
     
     
         32 . The method of  claim 21 , wherein the method comprises performing a plurality of sequencing reactions substantially simultaneously, and detecting the sequence of signals from the plurality of sequencing reactions. 
     
     
         33 . The method of  claim 32 , wherein a plurality of polymerizing agents, target nucleic acid molecules, or oligonucleotide primers are fixed directly or indirectly to the substrate in a predetermined pattern, and detecting the sequence of signals further comprises correlating the signal with a nucleic acid molecule corresponding to a predetermined position within that pattern. 
     
     
         34 . The method of  claim 33 , wherein the polymerizing agents, target nucleic acid molecules, or oligonucleotide primers are fixed to the substrate in the predetermined pattern in channels which have been etched in an orderly array. 
     
     
         35 . The method of  claim 33 , wherein the polymerizing agents, target nucleic acid molecules, or oligonucleotide primers are fixed to the substrate in the predetermined pattern by micropipetting droplets onto a substrate. 
     
     
         36 . The method of  claim 21 , wherein the sequence of signals is detected with a charge-coupled device (CCD) camera and converted into the nucleic acid sequence. 
     
     
         37 . The method of  claim 21 , wherein the sequence of signals is stored in a computer-readable medium. 
     
     
         38 . The method of  claim 21 , wherein the target nucleic acid molecule is present in a biological sample obtained from a subject. 
     
     
         39 . The method of  claim 21 , wherein the target nucleic acid molecule is present in a cell, and the exposing step comprises introducing the oligonucleotide primer and the probe into the cell. 
     
     
         40 . The method of  claim 39 , wherein the cell is present in a subject, and the introducing step comprises administering the oligonucleotide primer and the probe to a subject. 
     
     
         41 . The method of  claim 21 , wherein the target nucleic acid strand comprises one or more mutations associated with disease.