期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：9
页码：3758-3761
DOI：10.1073/pnas.74.9.3758
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A soluble extract prepared from HeLa cell nuclei has been shown to catalyze the 5'-terminal modification of RNA and synthetic polyribonucleotides to form m7G(5')pppA-and m7G(5')-pppG- structures referred to as caps. The reaction involves the transfer of a GMP moiety from GTP to the 5' end of an RNA molecule containing at least two terminal phosphates. Significantly, neither the beta nor the gamma phosphates of GTP are transferred and polynucleotides with no 5'-terminal phosphate or only one are not acceptors. In the absence of methyl donor, G(5')pppA- and G(5')pppG- structures were synthesized, indicating that methylation is not required for guanylylation. Cap formation was considered to occur by the following mechanism: (see article), in which AdoMet is S-adenosylmethionine, AdoHcy is S-adenosylhomocysteine, and (p)ppN- represents either the original 5' end of an RNA molecule or an internal site to which one or more phosphates were added after processing.
