One major objective is to elucidate how histone synthesis is regulated and how histones interact with DNA to form chromatin, not only during the presence of DNA replication in S phase cells but also during the absence of DNA replication in GI and GO (quiescent) cells. We have isolated some H2A cDNA clones which suggest that various specific mechanisms permit histone synthesis in quiescent cells to be from the same genes as used in proliferating cells. We are in the process of characterizing these mechanisms. We have also developed methodology which allows us to study soluble histone not bound to chromatin and to perform kinetic studies on the alterations in the level of soluble histone in different cell growth states and during changes in the rates of protein or DNA synthesis. Current biochemical characterization of soluble histone suggests that it is bound in a negatively charged complex that sediments at 8-9s. Isolating and characterizing the components involved in the complex but rigorous coordination of histone and DNA synthesis may lead to techniques or compounds of therapeutic value which disrupt this coordination in such a manner as to be selectively lethal to proliferating cells.
