Project 3: Mechanisms of Methyltransferase Dysregulation by Oncohistones

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PROJECT SUMMARY SUMMARY: The broad goal of this project is to study the detailed molecular mechanisms by which histone mutations associated with cancers perturb chromatin states, leading to disease. The next phase of this program is driven by our recent work with the Allis lab revealing a vastly expanded landscape of putative oncohistone mutations - over 4200 missense mutations in dozens of human cancers. Remarkably, the mutations occur in all four of the core histones and in both the N-terminal tails and globular histone fold domains. The very large number of newly identified oncohistones makes experimental characterization daunting. A key challenge is to identify those mutations that act as potential cancer drivers from those that are merely a consequence of the high mutation burden of a given tumor (i.e. passengers). We will work closely with other members of the P01 team to identify those mutations that most likely to fall into the former category and that, as such, merit in vivo testing. Strategically, we will approach this problem using newly developed high-throughput biochemical and yeast genetic screening tools (Aim 1) that are expected to identify mutations that alter chromatin stability and/or that affect the activity of trans-acting factors that operate on the chromatin polymer. Validation of the ‘hits’ from the screening studies will form the core of Aims 2 & 3 where we will combine the use of chemically-defined chromatin templates with biochemical, proteomic and genomic approaches to develop a mechanistic understanding of how select mutations impact chromatin state. In particular, we will study how breakdown in nucleosome symmetry, as a result of sub-stoichiometric incorporation of mutant histones, affects key processes such as chromatin remodeling and transcription. We imagine that many of the technologies developed in the context of this work will have broad utility in the epigenetics field generally. Ultimately, the biochemical knowledge base generated in the course of this program will motivate future therapeutic efforts for treating cancers associated with oncohistone mutants.