The objective of this research is to elucidate the functions of phosphorylated proteins and associated protein phosphorylation reactions in the cell nucleus. Currently proposed projects are concentrated on the study of several specific types of histone phosphorylation which are catalyzed by both cyclic AMP-dependent and cyclic AMP-independent protein kinases. Determination of the amino acid sequences in H1 histone surrounding the sites phosphorylated by a histone kinase found in growing cells will continue, and additional kinases catalyzing the phosphorylation of H1 and other histones will be sought. In addition, tissues will be examined for the presence of specific phosphatases catalyzing the dephosphorylation of particular phosphorylation sites. The effects of various types of histone phosphorylation on chromatin structure will be investigated by studying the nuclease susceptibility of reconstituted deoxynucleohistone and, in collaboration with others, by determining the effects of phosphorylation of histone-histone and DNA-histone interactions by circular dichroism, nuclear magnetic resonance and fluorescence anisotrophy. The activity of these reconstituted deoxynucleohistones as templates for RNA polymerase will also be studied in order to determine whether any structural changes caused by phosphorylation affect the transcribability of the DNA. Study of the phosphorylation of specific sites in H1 histone of growing and cyclic AMP-stimulated hepatoma cells will continue in order to clarify the relationship between the phosphorylation of particular sites and the processes of cell replication, growth and hormone response.