Identification of the Methylated Ribosomal Proteins in HeLa Cells and the Fluctuation of Methylation During the Cell Cycle

Methylated proteins from HeLa cell cytoplasmic ribosomes have been identified. At least seven proteins are methylated and four of them are mildly acidic. The nature of the methylated amino acid in each protein is presented. In synchronized HeLa cell culture, the extent of methylation for both subunits varies with the cell cycle. Methylation of the 40 S subunit occurs heavily in the late G1 phase whereas methylation of the 60 S subunit is most pronounced in the early S phase.