The present disclosure relates to a method of sequencing nascent RNA in a cell. In some embodiments, the nascent RNA is conjugated to DNA using copper-catalyzed azide-alkyne cycloaddition (CuAAC). Methods of the present disclosure can be used to generate genomic libraries of a cell and measure gene expression and enhancer and/or super-enhancer activity.

The present disclosure relates to a method of sequencing nascent RNA in a cell. In some embodiments, the nascent RNA is conjugated to DNA using copper-catalyzed azide-alkyne cycloaddition (CuAAC). Methods of the present disclosure can be used to generate genomic libraries of a cell and measure gene expression and enhancer and/or super-enhancer activity.

Provided in the present invention is an enzyme reaction solution for constructing a sequencing library and the use thereof. The enzyme reaction solution comprises an enzyme composition and a reaction buffer, wherein the enzyme composition comprises a nucleic acid endonuclease, a DNA polymerase, and a polynucleotide kinase; and the reaction buffer comprises a metal salt, a substrate, and a buffer medium aqueous solution. The present application aims to optimize the formulation of an enzyme reaction solution. The cleavage, terminal repair and addition of A to the terminal of a nucleic acid sample is achieved by a one-step reaction. In a suitable buffer system, the enzyme digestion reaction rate and the terminal repair reaction rate reach a balance. In the case where the initial amount of the sample is 100 pg to 1 .Math.g and the processing time is the same, a sequencing library with a consistent length distribution is obtained.

Provided is a linker element and a method of using the linker element to construct a sequencing library, wherein the linker element consists of a linker A and a linker B, the linker A is obtained through the complementary pairing of a long nucleic acid strand and a short nucleic acid strand, the 5′ end of the long strand has a phosphoric acid modification, and the 3′ end of the short strand has an enclosed modification, with enzyme sites in the short strand; and the linker B is a nucleic acid single strand, and the 3′ end thereof can be in a complementary pairing with the 5′ end of the long strand of the linker A. Using the linker element of the present invention for constructing a sequencing library ensures the linking directionality of the linkers while solving the problems of fragment interlinking, linker self-linking and low linking efficiency, and reducing the purification reaction between steps, shortening the linking time and reducing costs.

Methods for in situ amplification (ISA) of cfNA, such as cfDNA, in a sample are provided wherein the cfNA in the sample is not subject to a nucleic acid purification step. The methods disclosed may be used to generate an analyzable pool of cfNA present in the sample. The analyzable pool may be used with a variety of analytical techniques to characterize the nucleic acid in the sample. Methods of diagnosis, determining a therapeutic intervention and monitoring of a subject are also provided.

The present disclosure relates to a method of sequencing nascent RNA in a cell. In some embodiments, the nascent RNA is conjugated to DNA using copper-catalyzed azide-alkyne cycloaddition (CuAAC). Methods of the present disclosure can be used to generate genomic libraries of a cell and measure gene expression and enhancer and/or super-enhancer activity.

The present disclosure relates to a method of enzymatically repairing RNAs that are nicked or at least partially cleaved. The method comprises providing a biological sample containing RNAs that are nicked or at least partially cleaved; purifying the nicked or at least partially cleaved RNAs contained in the biological sample, under a non-denaturing condition, to remove non-RNA components; and treating the purified RNAs with at least one of the following: (i) one or more enzymes that exhibit the activity of an RNA 3 phosphatase or cyclic phosphatase and the activity of an RNA 5 kinase, and an RNA ligase, or (ii) a 3-5 RNA ligase, thereby forming repaired RNAs from the nicked or at least partially cleaved RNA. The present disclosure also relates to a method of detecting RNAs by enzymatically repairing RNAs that are nicked or at least partially cleaved, and detecting the repaired RNAs.

Provided is a linker element and a method of using the linker element to construct a sequencing library, wherein the linker element consists of a linker A and a linker B, the linker A is obtained through the complementary pairing of a long nucleic acid strand and a short nucleic acid strand, the 5 end of the long strand has a phosphoric acid modification, and the 3 end of the short strand has an enclosed modification, with enzyme sites in the short strand; and the linker B is a nucleic acid single strand, and the 3 end thereof can be in a complementary pairing with the 5 end of the long strand of the linker A. Using the linker element of the present invention for constructing a sequencing library ensures the linking directionality of the linkers while solving the problems of fragment interlinking, linker self-linking and low linking efficiency, and reducing the purification reaction between steps, shortening the linking time and reducing costs.

Provided herein are compositions for and methods of generating ligation-competent nucleic acids. In some aspects, the compositions comprise Exonuclease III, T4 DNA Polymerase, Klenow, and/or T4 polynucleotide kinase.

Methods for in situ amplification (ISA) of cfNA, such as cfDNA, in a sample are provided wherein the cfNA in the sample is not subject to a nucleic acid purification step. The methods disclosed may be used to generate an analyzable pool of cfNA present in the sample. The analyzable pool may be used with a variety of analytical techniques to characterize the nucleic acid in the sample. Methods of diagnosis, determining a therapeutic intervention and monitoring of a subject are also provided.