Our main objectives are to continue our studies on poly ADP-ribose polymerase along two broad lines: (1)\dealing with relationships between poly ADP-ribosylation of chromosomal proteins and functions in chromatin; and (2)\continuing our studies on the overall importance of this nuclear protein modification on chromatin structure and architecture. The intention of the past year's work has been to determine basic biochemical properties of poly (ADP-Rib) by immunological enrichment and to characterize these chromatin domains and study them specifically with regard to modification of histone H1. Three aims have been developed: (1)\to develop an immunological fractionation method and subsequently to characterize the DNA associated with poly (ADP-Rib) nucleosomes; (2)\to study poly (ADP-Rib) crosslinking of chromatin--does it occur in vivo?; and (3)\to study the nature of the polypeptide domains of H1 with respect to its poly (ADP-Rib) induced crosslinking. Progress has been made in each of the areas listed above. The strategy of our laboratory during the last year has been to approach poly ADP-ribosylation at the oligonucleosomal level of chromatin and to systematically catalogue: (1)\how to immunologically enrich for these chromatin domains; (2)\determine what is unique about these domains with respect to DNA sequences and transcriptional domains; (3)\determine other past-translational modifications; and (4)\determine the mechanism of H1 crosslinking. These topics were studied independently and each has, in part, progressed to some extent. We believe that this work has provided fundamental information about not only poly (ADP-Rib), but also chromatin, per se. The biological function of poly (ADP-Rib) relating to DNA strand breaks is under a separate study under an independent support from this application. (K)