Synthesis of tagged nucleic acids

A method comprising:

• (A) providing:
• a sample containing one or more RNA molecules of interest;
• at least one RNA-dependent DNA polymerase;
• a terminal tagging oligoribonucleotide comprising ribonucleotides (rTTO), which terminal tagging oligoribonucleotide comprises a 5′-portion and 3′-portion, wherein the 5′-portion exhibits a sequence that is complementary to the sequence of a DNA sequence tag that it is desired to join to the 3′-termini of first-strand cDNA molecules, and wherein the 3′-portion comprises at least three random nucleotides, of which the 3′-terminal nucleotide is blocked so that it is not capable of being extended by a DNA polymerase;
• a second-strand cDNA synthesis primer, comprising an oligodeoxyribonucleotide that comprises a 5′-portion and a 3′-portion, wherein the 5′-portion exhibits at least a portion of an anti-sense promoter sequence for a double-stranded RNA polymerase promoter, and the 3′-portion has a 3′-hydroxyl group and exhibits a sequence that is complementary to the DNA sequence tag that it is desired to be joined to the 3′-termini of the first-strand cDNA molecules;
• and
• an RNA polymerase that is capable of synthesizing RNA using a DNA template that is joined to a double-stranded RNA polymerase promoter, wherein the 3′-terminus of the template strand exhibits a sequence that is complementary to the anti-sense promoter sequence exhibited by the 5′-portion of the second-strand cDNA synthesis primer;
• (B) incubating a solution containing the sample with the one or more RNA molecules of interest, plus at least one of the at least one RNA-dependent DNA polymerases, under conditions and for sufficient time wherein first-strand cDNA molecules that are complementary to the RNA molecules of interest are synthesized;
• (C) incubating the solution from step (B) under conditions and for sufficient time wherein RNA that is annealed to DNA and single-stranded RNA are degraded;
• (D) incubating the solution from step (C) containing the first-strand cDNA molecules, plus the terminal tagging oligoribonucleotide and at least one of the at least one RNA-dependent DNA polymerases, under conditions and for sufficient time wherein the terminal tagging oligoribonucleotide anneals to the first-strand cDNA molecules and the 3′-termini of the first-strand cDNA molecules are extended using the terminal tagging oligoribonucleotide as a template, wherein first-strand cDNA molecules that have the DNA sequence tag joined to their 3′-termini are synthesized, and then incubating the solution under conditions and for sufficient time wherein RNA that is annealed to DNA and single-stranded RNA are degraded;
• (E) incubating the solution from step (D) containing the first-strand cDNA molecules that have the DNA sequence tag joined to their 3′-termini, plus the second-strand cDNA synthesis primer and either at least one of the at least one RNA-dependent DNA polymerases or the DNA-template-specific DNA polymerase, under conditions and for sufficient time wherein double-stranded cDNA molecules that contain a double-stranded RNA polymerase promoter that is recognized by the RNA polymerase are synthesized;
• (F) incubating the solution from step (E) containing double-stranded cDNA molecules, plus the RNA polymerase that recognizes and binds the double-stranded RNA polymerase promoter, under conditions and for sufficient time wherein multiple copies of sense RNA molecules are synthesized, each of which exhibits substantially the same sequence as one of the one or more RNA molecules of interest in the sample and has an RNA sequence tag joined to its 5′-terminus;
• (G) further providing:
• the sense RNA molecules that have the RNA sequence tag joined to their 5′-termini from step (F);
• a second-round first-strand cDNA synthesis primer comprising one or more oligonucleotides, at least one of which is complementary to each of the sense RNA molecules that have the RNA sequence tag joined to their 5′-termini that are provided in step (G);
• at least one RNA-dependent DNA polymerase;
• a second-round second-strand cDNA synthesis primer, comprising an oligodeoxyribonucleotide that has a 5′-portion and a 3′-portion, wherein the 5′-portion exhibits at least a portion of an anti-sense promoter sequence for a double-stranded RNA polymerase promoter, and the 3′-portion has a 3′-hydroxyl group and exhibits a sequence that is complementary to the DNA sequence tag that is joined to the 3′-termini of the first-strand cDNA molecules from step (D);
• an RNA polymerase that is capable of synthesizing RNA using a DNA template that is joined to a double-stranded RNA polymerase promoter that exhibits, on the 3′-terminus of the template strand, the sense promoter sequence of the double-stranded RNA polymerase promoter that, at least a portion of which, is complementary to the anti-sense promoter sequence exhibited by the 5′-portion of the second-round second-strand cDNA synthesis primer;
• (H) incubating a solution containing the sense RNA molecules that have the RNA sequence tag joined to their 5′-termini, plus the second-round first-strand cDNA synthesis primers and at least one of the at least one RNA-dependent DNA polymerases, under conditions and for sufficient time wherein the second-round first-strand cDNA synthesis primers anneal to the sense RNA molecules that have the RNA sequence tag joined to their 5′-termini and second-round first-strand cDNA molecules that have the DNA sequence tag joined to their 3′-termini are synthesized;
• (I) incubating the solution from step (H) under conditions and for sufficient time wherein RNA that is annealed to DNA is degraded;
• (J) incubating a solution containing the second-round first-strand cDNA molecules that have the DNA sequence tag joined to their 3′-termini, plus the second-round second-strand cDNA synthesis primer and either at least one of the at least one the RNA-dependent DNA polymerases or the DNA-template-specific DNA polymerase, under conditions and for sufficient time wherein second-round double-stranded cDNA molecules that contain a double-stranded RNA polymerase promoter are synthesized;
• and
• (K) incubating the solution from step (J), containing second-round double-stranded cDNA molecules, plus the second-round RNA polymerase, under conditions and for sufficient time wherein multiple copies of sense RNA molecules are synthesized, each of which, exhibits substantially the same sequence as one of the one or more RNA molecules of interest in the sample and has the RNA sequence tag joined to its 5′-terminus.