DESCRIPTION (provided by applicant): A research program will be undertaken to deepen our understanding of the molecular mechanisms underlying the regulation of chromatin structure and function. Chromatin, the complex of genomic DNA with histone and non-histone proteins, is the physiologically relevant form of all eukaryotic genomes. Once thought of as merely a packaging solution for the DNA, it is now accepted that chromatin serves as a dynamic signaling platform to regulate DNA access. Indeed, this research proposal is rooted in the idea that there exist heritable functional "states" of chromatin, representing a fundamental regulatory mechanism that operates outside of the DNA itself, that help set the transcriptional potential of a gene locus. Mistakes made in establishing and maintaining these chromatin states, governed by chromatin remodeling activities, lead to the misregulation of genes with far-reaching implications for human biology and human disease. Building on some recent breakthroughs on the synthesis and application of what we call 'designer chromatin', we will integrate chemical, biochemical, biophysical and genetic tools for the purpose of obtaining a deeper understanding of the physicochemical principles underlying the regulation of chromatin function. The immediate focus will be on the role of histone ubiquitylation in chromatin biology (aims 1 and 2), however, new tools will also be developed that broaden the scope of this work significantly into other aspects of chromatin regulation and, importantly, that do so by greatly accelerating mechanistic biochemistry (aims 2 and 3). In the short term, this research is designed to reveal the molecular mechanism(s) by which histone ubiquitylation orchestrates downstream biochemistry on chromatin, an understanding that may aid the rational design of therapeutics directed at inhibiting enzymes such as the methyltransferase, hDot1L, for the treatment of leukemias. In the long term, the technologies that will be developed as part of this work, will have broad utility in the chromatin area. .

PUBLIC HEALTH RELEVANCE: DNA in eukaryotic cells is packaged into chromatin, the fundamental unit of which is the nucleosome in which DNA is wrapped around a spool of proteins called histones. The packaging of nucleosomes into higher-order chromatin structures is a key determinant of gene expression, and posttranslational modification of histone proteins is one way that chromatin structure is manipulated (1). The proposed research program is expected to reveal the molecular mechanism(s) by which one such modification, histone ubiquitylation, controls gene transcription through the recruitment and activation of effector proteins such as lysine methyltransferases. Such an understanding may aid the rational design of therapeutics directed at inhibiting these enzymes for the treatment of leukemias. Moreover, the high through-put technologies that will be developed as part of this program, will have broad utility in the chromatin biology area.