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 molecules^1–9. 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′ structure^10,11. 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 mRNAs^2–9. 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 vitro^5–8 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 genome^12,13.