Methylated nucleotides block 5' terminus of HeLa cell messenger RNA.

来自 dx.doi.org

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294

作者：

CM Wei，A Gershowitz，B Moss

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摘要：

Polyadenylylated [poly(A) +] mRNA from HeLa cells that were labeled with [ 3H-methyl]-methionine and 14C-uridine was isolated by poly(U)-Sepharose chromatography. The presence of approximately two methyl groups per 1000 nucleotides of poly(A) + RNA was calculated from the 3H/ 14C ratios and known degrees of methylation of 18S and 28S ribosomal RNAs. All four 2′-0-methylribonucleosides, but only two basemethylated derivatives, 7-methylguanosine (7MeG) and 6-methyladenosine (6MeA), were identified. 6MeA was the major component accounting for approximately 50% of the total methyllabeled ribonucleosides. 7MeG, comprising about 10% of the total, was present exclusively at the 5′ terminus of the poly(A) + RNA and could be removed by periodate oxidation and β elimination. Evidence for a 5′ to 5′ linkage of 7MeG to adjacent 2′-0-methylribonucleosides through at least two and probably three phosphates to give structures of the type 7MeG 5′ppp 5′NMep- and 7MeG 5′ppp 5′NMepNmep- was presented. The previous finding of similar sequences of methylated nucleotides in mRNA synthesized in vitro by enzymes associated with virus cores indicates that blocked 5′ termini may be a characteristic feature of mRNAs that function in eucaryotic cells.

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关键词：

Humans Hela Cells Tritium Carbon Radioisotopes Phosphoric Diester Hydrolases Alkaline Phosphatase RNA, Neoplasm Nucleotides Adenosine Guanosine