Synthesis and degradation of H1 histone subtypes in mouse lymphoma L5178Y cells

H1 histone of mouse lymphoma L5178Y was fractionated into five subtypes, I-V, by Bio-Rex 70 column chromatography. The rates of synthesis of subtypes III and V were higher than those of I, II, and IV, as determined by the measurement of [3H]lysine incorporation. The degradation of the subtype was estimated assuming first order kinetics; subtypes III and V had half-lives of 18 h and 25 h, respectively, and the three other subtypes all had half-lives of 63 h. The syntheses of these subtypes during the cell cycle were examined using synchronized cultures. The syntheses of subtypes I, II, and IV started at the beginning of S phase, whereas those of III and V started in mid-S phase. The syntheses of III and V were at least 1.5-2 times more rapid than those of I, II, and IV, and their active synthesis was accompanied by their rapid degradation. The five subtypes of H1 were further characterized in relation to phosphorylation. Each showed characteristic differences in its synthetic pattern or phosphorylation, and we concluded that each H1 subtype has its own specific function at least in the process of replication of chromatin.