Poly 2′-O-methylcytidylic acid and the role of the 2′-hydroxyl in polynucleotide structure

Abstract

In the presence of Mn ++ cations, 2′-O-methylcytidine-5′-pyrophosphate is readily polymerized by polynucleotide phosphorylase. The neutral form of the resulting poly 2′-O-methylcytidylic acid more closely resembles the neutral, single-stranded form of poly rC than poly dC. The polymer forms a twin-stranded helix in the same pH range as poly rC, but not poly dC, showing that formation of the acid form of poly rC does not involve hydrogen bonding of the 2′-OH to a base residue or phosphate oxygen. Poly 2′-O-MeC also forms a double-stranded helix with poly rI. Implications as to the role of the 2′-OH in polynucleotide structure are briefly discussed.