Involvement of the Change in Chromatin Structure in Thymocyte Apoptosis Induced by Phosphorylation of Histones

: The inhibitors of protein phosphatase such as calyculin A and okadaic acid induced thymocyte apoptosis. DNA fragmentation was increased in the nuclei from thymocytes treated with calyculin A, which accelerated phosphorylation of histones. Judging from the circular dichroism analysis, the structure of soluble chromatin was changed by the treatment with calyculin A. These results suggest that the change in chromatin structure may be one of the molecular mechanisms of internucleosomal DNA fragmentation.