We propose to examine changes in the levels of modification of chromatin proteins which are associated with age. The modifying elements to be studied are acetylation and phosphorylation of the various fractions of histones. The investigation will include analysis of the modifications of the individual histones as well as the enzymology associated with such modifications. Comparison will be made between the age-related changes in such chromatin protein modification in post-mitotic cells such as brain neurons and in cells with a low level of mitotic turnover such as those of liver.