Absence of metabolic turnover of N-methyl groups in non-histone and high mobility group chromosomal proteins

Turnover of N-methyl groups in non-histone chromosomal (NHC) and high mobility group (HMG) proteins from chinese hamster ovary cell nuclei was compared with that of the peptide backbone. Cells grown with tritiated amino-acids and methionine (Me-14C) were resuspended in unlabeled medium, and aliquots removed at 4 time points. Halflives were calculated from the decay of the respective specific activities by the method of least squares. Ratios of halflives for 14C and 3H calculated from the first order rate decay curves of the specific activities were shown to be close to unity.