Identification and mapping of N⁶-methyladenosine containing sequences in Simian Virus 40 RNA

Abstract

Late SV40 16S and 19S mRNAs were found to contain an average of three m6A residues per mRNA molecule. The methylated residues of both the viral and cellular mRNAs occur in two sequences; Gpm6ApC and (Ap)nm6ApC, where n = 1-4. More than 60% of the m6A residues in SV40 16S and 19S mRNAs occur in Gpm6ApC even though there are twice as many (A)nAC than GAC sequences in these messengers. The m6A containing oligonucleotides of late SV40 MRNAs were localized in the viral messengers. In the 16S mRNA two m6A oligonucleotides were located at the 5' coding region between 0.95--0.0 map units. The third m6A residue was mapped between 0.0--0.14 map units in the translated portion of this mRNA. The overall pattern of internal methylation in the 19S mRNA is similar. However, some differences between 16S and 19S mRNAs were observed in both the content and location of the longer (Ap)n m6AC nucleotides. These results provide the first example of precise localization of internal methylation sequences in mRNA species with defined coding specificity. It implies that a) location of m6A residues is not random but specific to a particular region of the RNA, b) apart from sequence specificity other structural features of the mRNA may influence internal methylation and c) m6A residues are present in coding regions of SV40 mRNAs.

Nonmuscle and muscle tropomyosin isoforms are expressed from a single gene by alternative RNA splicing and polyadenylation.

“…In no case did we detect both the 1.1-and 1.3-kb transcripts in the same cell type, nor did we observe mRNA containing combinations of the tissuespecific exons, i.e., fibroblast with skeletal muscle. These results clearly indicate that utilization of tissue-specific methylation (11,23,84,98); and (iii) trans-acting factors such as proteins and small nuclear RNAs (6,47,66,76). At the nucleotide sequence level, all introns within genes encoding proteins have a well-defined consensus sequence at the 5' and 3' boundaries (7,65,86).…”

Precise localization of m6A in Rous sarcoma virus RNA reveals clustering of methylation sites: implications for RNA processing.

“…(SV40) late mRNAs, on the other hand, each contain an average of three m6As, all near the 5' ends of those messages in translated sequences (7). Adenovirus mRNAs are methylated in the 5' two-thirds of the molecules, and m6As seem, in this system, to be conserved during mRNA processing (9,33).…”

“…Secondary effects of the drugs have not been ruled out. Furthermore, the requirement for internal methylation in mRNA is not absolute, as mature messages without any detectable m6A residues do exist, including globin and histone mRNAs (24,27).In all cases characterized to date, m6A occurs only in the sequences Gm6AC and Am6AC (7,12,31,38). Preliminary localization studies with specific RNAs have determined that the distribution of m6A within a molecule is nonrandom.…”

“…In all cases characterized to date, m6A occurs only in the sequences Gm6AC and Am6AC (7,12,31,38). Preliminary localization studies with specific RNAs have determined that the distribution of m6A within a molecule is nonrandom.…”

Publisher's Note

“…The presence of m 6 A in viral RNA has, indeed, been known for decades, having been observed in B77 avian sarcoma virus, Rous sarcoma virus, simian virus 40, influenza, and adenoviruses in the 1970s. [42][43][44][45][46] However, akin to the case with mRNA, the functions and regulation of RNA modifications in host-virus interactions have only recently begun to be unveiled. HIV-1 is a very illustrative example of this, as it exploits multiple RNA modifications to its advantage.…”