Newcastle disease virus mRNA lacks 2'-O-methylated nucleotides.

Abstract

MESSENGER RNA molecules from various sources contain methylated nucleotides at the 5′ terminus of the RNA molecules1–9. The structure at the 5′ terminus of most cellular and viral mRNAs consists of a terminal base-methylated nucleotide linked to a ribose-methylated nucleotide through a 5′ to 5′ pyrophosphate bond, such as m7G(5′)ppp(5′)AmpNp or m7(5′)ppp(5′)GmpNp. Initiation and subsequent in vitro translation of mRNA are dependent on the presence of m7G in a blocked 5′ structure10,11. Thus, methylation (m7G) seems to serve an important function in the translation (and/or control) of viral and cellular mRNA. The role of 2′-O-methylation has not been identified. The widespread presence of 2′-O-methylation in mRNA from diverse systems suggested that they might be a common feature of all eukaryotic mRNAs2–9. We report here that the 5′-terminal structure of Newcastle disease virus (NDV) mRNA synthesised in vitro is m7G(5′)ppp(5′)GpPyp. The structure isolated from NDV mRNA differs from those reported for all other mRNAs synthesised in vitro5–8 in that the RNA lacks 2′-O-methylated nucleotides. During the preparation of our report we learned that the 40S RNA genome of Sindbis virus14 and the 26S RNA synthesised in Sindbis virus-infected cells15 have the structure m7G(5′)pppNp. In addition tobacco mosaic virus has m7G(5′)ppp(5′)Gp at the 5′ end of the viral genome12,13.