| Summary: | 碩士 === 國立陽明大學 === 生物藥學研究所 === 90 === Post-translational modifications play pivotal roles in almost all cellular processes. In contrast to the large number of studies in protein phosphorylation, evidences for the functional roles of protein methylation are just now accumulating. Arginine methylation has been recently implicated as a novel mechanism in cell growth control, gene expression regulation, signal transduction and protein intracellular localization. In this study, we examined whether protein methylation, with particular attention on arginine methylation, played a role in the differentiation of K-562 cells induced by Ara-C. Our results showed that methylation of selective endogenous protein substrates were modulated during differentiation and the methyltransferase activity torward hnRNP A2 was upregulated and reached its peak at 48-72hr after Ara-C treatment suggesting that differentiation of K562 into erythroid involved dynamic methylation/ demethylation of particular proteins. Methylation of hnRNP A2 and a number of the endogenous substrates was inhibited in the presence of the GR peptide (GGRGGRGRGGF) but not the GA peptide whose arginines were replaced by alanines. This indicated that the methyl groups were incorporated predominantly into arginine residues. AdOx, a potent inhibitor of methyltransferases, suppressed differentiation of K562 as measured by benzidine staining. Our results suggested a crucial role of protein arginine methylation in K562 differentiation into erythroid. We also showed that calcium, which has been shown to play roles in K562 differentiation, differentially modulated methylation of endogenous protein substrates in K562 cells suggesting that regulation of arginine methyltransferase activity during K562 differentiation may be mediated by calcium signaling.
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