Sequential methylation of globin mRNA in nucleated erythroid cells and reticulocytes of mice

The order of methylation of the 5'-terminus of globin mRNA of mice was studied by incubation of staged nucleated erythroid cells and peripheral reticulocytes with [methyl-3H] methionine. Methylation of the 5'-termini of alpha and beta- globin mRNAs in enucleated reticulocytes was demonstra...

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Bibliographic Details
Published in:The Journal of biological chemistry 1978-01, Vol.253 (1), p.246-251
Main Authors: T Cheng, H H Kazazian, Jr
Format: Article
Language:English
Subjects:
Animals
Globins - biosynthesis
Globins - genetics
Male
Methionine - metabolism
Methylation
Mice
Reticulocytes - metabolism
RNA, Messenger - metabolism
Spleen - metabolism
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Summary:The order of methylation of the 5'-terminus of globin mRNA of mice was studied by incubation of staged nucleated erythroid cells and peripheral reticulocytes with [methyl-3H] methionine. Methylation of the 5'-termini of alpha and beta- globin mRNAs in enucleated reticulocytes was demonstrated as follows: (a) [methyl-3H] incorporation into poly(A)+ RNA of reticulocytes co-migrated with the alpha- and beta- globin mRNAs on gel electrophoresis, and (b) following digestion of this RNA, radioactivity was localized to the four methyl sites at the 5'-capped structure of mouse globin mRNAs. However, this methylation is only 5 to 8% as efficient as in nucleated erythroid precursor cells, suggesting that most globin mRNA molecules are fully methylated prior to the reticulocyte stage. Incubations of early and late nucleated erythroid precursor cells and pulse-chase experiments with reticulocytes demonstrate that addition of the four 5'-terminal methyl groups follows an orderly sequence. In addition, the pulse-chase experiments suggest the turnover of the N7-methyl group on the 5'-terminal guanosine, but not of the other methyl groups in the 5'-terminus of globin mRNA. Thus, 5'-terminal methylation of globin mRNA is a nonrandom, dynamic process.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(17)38296-0