Template-free enzymatic synthesis of polynucleotides using poly(A) and poly(U) polymerases
The present invention is directed to methods and compositions for template-free enzymatic synthesis of a polyribonucleotide of a predetermined sequence from 3′-O-reversibly blocked nucleoside triphosphates using poly(A) and poly(U) polymerases.
1 . A kit for performing template-free synthesis of a polyribonucleotide having a predetermined sequence, the kit comprising a poly (A) polymerase (PAP), an initiator attached to a solid support, and 3′-O-blocked ribonucleoside triphosphate monomers,
wherein the PAP comprises a PAP variant having an amino acid sequence that is at least 90 percent identical to the amino acid sequence of SEQ ID NO: 3, wherein the PAP variant comprises a substitution of the methionine at position 318 and a substitution of the valine at position 240 with respect to SEQ ID NO: 3, and
wherein the PAP variant is capable of (a) synthesizing a ribonucleic acid fragment without a template and (b) incorporating a 3′-O-azidomethyl-ribonucleoside triphosphate into a ribonucleic acid fragment or a 3′-O-azidomethyl-2′-deoxyribonucleoside triphosphate into a deoxyribonucleic acid fragment.
2 . The kit of claim 1 , wherein said 3′-O-protected ribonucleoside triphosphate monomers comprise one or more of 3′-O-azidomethyl-riboadenosine triphosphate, 3′-O-azidomethyl-riboguanosine triphosphate, 3′-O-azidomethyl-ribocytidine triphosphate, 3′-O-azidomethyl-ribothymidine triphosphate and 3′-O-amino-ribouridine triphosphate.
3 . A poly (A) polymerase (PAP) variant comprising an amino acid sequence that is at least 90 percent identical to SEQ ID NO: 3 wherein the PAP variant comprises a substitution of the methionine
at position 318 and a substitution of the valine at position 240 with respect to SEQ ID NO: 3,
wherein the PAP variant is capable of (a) synthesizing a ribonucleic acid fragment without a template and (b) incorporating a 3′-O-azidomethyl-ribonucleoside triphosphate into a ribonucleic acid fragment or a 3′-O-azidomethyl-2′-deoxyribonucleoside triphosphate into a deoxyribonucleic acid fragment.
4 . The PAP variant of claim 3 , wherein said substitution of the methionine at position 318 is selected from F, Y, V, E or T.
5 . The PAP variant of claim 3 wherein said substitution of the valine at position 240 is alanine or glycine.
6 . The PAP variant of claim 3 , wherein said substitution of the methionine at position 318 is T and said substitution of the valine at position 240 is A.
7 . The PAP variant of claim 6 , further comprising a substitution of the alanine at position 410 relative to SEQ ID NO: 3.