RT Journal Article SR Electronic T1 Base Pairing and Functional Insights into N3-methylcytidine (m3C) in RNA JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.08.27.270322 DO 10.1101/2020.08.27.270322 A1 Mao, Song A1 Haruehanroengra, Phensinee A1 Ranganathan, Srivathsan V. A1 Shen, Fusheng A1 Begley, Thomas J. A1 Sheng, Jia YR 2020 UL http://biorxiv.org/content/early/2020/08/28/2020.08.27.270322.abstract AB N3-methylcytidine (m3C) is present in both eukaryotic tRNA and mRNA and plays critical roles in many biological processes. We report the synthesis of the m3C phosphoramidite building block and its containing RNA oligonucleotides. The base-pairing stability and specificity studies show that the m3C modification significantly disrupts the stability of the Watson-Crick C:G pair. Further m3C decreases the base pairing discrimination between C:G and the other mismatched C:A, C:U, and C:C pairs. Our molecular dynamic simulation study further reveals the detailed structural insights into the m3C:G base pairing pattern in an RNA duplex. More importantly, the biochemical investigation of m3C using reverse transcription shows that N3-methylation specifies the C:A pair and induces a G to A mutation using HIV-1-RT, MMLV-RT and MutiScribeâ„¢-RT enzymes, all with relatively low replication fidelity. For other reverse transcriptases with higher fidelity like AMV-RT, the methylation could completely shut down DNA synthesis.Competing Interest StatementThe authors have declared no competing interest.