Decrease in uH2A (protein A24) of a mouse temperature-sensitive mutant.

ts85 cell is a temperature-sensitive mutant of cell cycle, and chromosomal protein uH2A of this mutant disappears at the non-permissive temperature. uH2A in nucleosomes is thought to be synthesized or degradated as follows. H2A + Ubiquitin in equilibrium uH2A. Up to date, the degradation of uH2A was shown to be catalyzed by uH2A lyase, however no enzymes (factors) concerning its synthesis have been elucidated. Here, we show that ATP is prerequisite for the synthesis of uH2A, and that the disappearance of uH2A at the non-permissive temperature may be due to a reduction in the rate of synthesis rather than an increase in the rate of its degradation.