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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.
Insights
Late SV40 16S and 19S mRNAs contain N6-methyladenosine (m6A) residues, primarily in Gpm6ApC sequences. These methylation sites are specifically located within the coding regions of viral messengers, not randomly distributed.
Area of Science:
- Molecular Biology
- RNA Methylation
- Virology
Background:
- N6-methyladenosine (m6A) is a prevalent RNA modification influencing gene expression.
- The precise location and functional significance of m6A in viral mRNA remain areas of active investigation.
Purpose of the Study:
- To investigate the occurrence, sequence context, and localization of m6A residues in late Simian Virus 40 (SV40) 16S and 19S mRNAs.
- To determine if m6A methylation is randomly distributed or specifically targeted within viral mRNA coding regions.
Main Methods:
- Analysis of late SV40 16S and 19S mRNAs to identify and quantify m6A residues.
- Determination of the sequence context of methylated adenosine residues.
- Localization of m6A-containing oligonucleotides within the viral mRNA molecules using mapping techniques.
Main Results:
- Late SV40 16S and 19S mRNAs contain an average of three m6A residues per molecule.
- Methylated residues predominantly occur in Gpm6ApC and (Ap)nm6ApC (n=1-4) sequences.
- Over 60% of m6A residues were found in Gpm6ApC sequences, despite a higher abundance of (A)nAC sequences.
- m6A residues were precisely localized within the 5' coding regions and translated portions of both 16S and 19S mRNAs.
- Differences in m6A content and location of longer (Ap)n m6AC nucleotides were observed between 16S and 19S mRNAs.
Conclusions:
- m6A methylation in SV40 mRNAs is not random but occurs at specific locations within coding regions.
- Both sequence specificity and other mRNA structural features likely influence the internal methylation pattern.
- These findings provide the first precise localization of internal methylation sequences in mRNA species with defined coding specificity, suggesting functional implications for viral gene expression.