METABOLISM OF HISTONE FRACTIONS .I. SYNTHESIS OF HISTONE FRACTIONS DURING LIFE CYCLE OF MAMMALIAN CELLS

The histone fractions f1, f2a1, f2a2, f2b, and f3 have been isolated from suspension tissue cultures of Chinese hamster cells. Amino acid analysis and polyacrylamide gel electrophoresis demonstrated that these Chinese hamster histone fractions are similar to calf thymus histone fractions obtained by the same method. Using the doublethymidine blockade method, Chinese hamster cultures were synchronized in their life cycle. The synthesis of all five histone fractions was clearly demonstrated to occur mainly in the S phase, each histone fraction being synthesized concomitantly with the other four fractions and accumulating in chromatin concomitantly with the increase in mass of DNA. A significant synthesis of all five histone fractions was also observed when DNA synthesis was inhibited in synchronized cultures by thymidine, suggesting the possibility that histones turn over in chromatin during thymidine block. © 1968.