Alterations in gene expression cause numerous cancers including ovarian, bladder, breast and colorectal tumors, as well as neurodegenerative conditions, such as Alzheimer's disease. The dynamic organization of the human genome into chromatin regulates transcription initiation and elongation, while defects in chromatin modifications, assembly, disassembly and remodeling results in the misregulation of many oncogenes. This has led to chromatin modifying complexes becoming one of the main chemotherapeutic drug targets. Numerous studies have identified and correlated the components involved in chromatin transcriptional regulation (CTR), which include histone variants, histone post-translational modifications (PTMs), histone chaperone assembly factors and chromatin remodeling factors. Remarkably, genetic, biochemical, structural and deep sequencing studies have not fully revealed the mechanisms of CTR. We hypothesize that nucleosome unwrapping, histone PTMs, histone variants, histone chaperones and chromatin remodelers function together to significantly influence TF occupancy and H2A-H2B heterodimer exchange to regulate transcription. We have developed precise chemical tools and single molecule measures capable of determining the mechanisms and functions of CTR. Using these methodologies, we will determine the mechanisms by which histone variants, PTMs, chaperones and chromatin remodeling complexes function together to cooperatively (additively and multiplicatively), anti-cooperatively and redundantly regulate transcription. We propose in the renewal application the following Specific Aims: (1) Determine the mechanisms by which nucleosomes influence transcription factor dynamics;(2) Determine the transcriptional regulatory mechanisms of H2A.Z, H3.3 and nucleosome entry-exit PTMs. (3) Determine the transcriptional regulator mechanisms behind H2A-H2B heterodimer exchange and removal. These studies will provide a foundation for understanding the mechanisms and functional interactions behind chromatin transcriptional regulation and the misregulation of numerous oncogenes.

Public Health Relevance

Regulation of gene expression and genomic stability by epigenetic factors such as histone modifications, histone variants and nucleosome dynamics have become a dominant field in cancer epigenetics because of the reversible nature of epigenetic alterations. Recent advances in understanding epigenetic factors have led to the emergence of epigenetic therapy and the recent FDA approval of multiple epigenetic drugs for cancer treatment. This proposal uses a combination of advanced protein chemistry and single molecule approaches to reveal the molecular mechanisms behind the function of chromatin epigenetic regulators. These studies will provide molecular information for understanding drug resistance, tumorigenesis, and for designing new cancer drugs and therapies.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Macromolecular Structure and Function C Study Section (MSFC)
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Preusch, Peter C
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Ohio State University
Schools of Arts and Sciences
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North, Justin A; Šimon, Marek; Ferdinand, Michelle B et al. (2014) Histone H3 phosphorylation near the nucleosome dyad alters chromatin structure. Nucleic Acids Res 42:4922-33
Luo, Yi; North, Justin A; Rose, Sean D et al. (2014) Nucleosomes accelerate transcription factor dissociation. Nucleic Acids Res 42:3017-27
North, Justin A; Amunugama, Ravindra; Klajner, Marcelina et al. (2013) ATP-dependent nucleosome unwrapping catalyzed by human RAD51. Nucleic Acids Res 41:7302-12
Sen, Payel; Vivas, Paula; Dechassa, Mekonnen Lemma et al. (2013) The SnAC domain of SWI/SNF is a histone anchor required for remodeling. Mol Cell Biol 33:360-70
Gao, Min; Nadaud, Philippe S; Bernier, Morgan W et al. (2013) Histone H3 and H4 N-terminal tails in nucleosome arrays at cellular concentrations probed by magic angle spinning NMR spectroscopy. J Am Chem Soc 135:15278-81
Law, Yu Kay; Forties, Robert A; Liu, Xin et al. (2013) Sequence-dependent thymine dimer formation and photoreversal rates in double-stranded DNA. Photochem Photobiol Sci 12:1431-9
Shimko, John C; Howard, Cecil J; Poirier, Michael G et al. (2013) Preparing semisynthetic and fully synthetic histones h3 and h4 to modify the nucleosome core. Methods Mol Biol 981:177-92
Kodgire, Prashant; Mukkawar, Priyanka; North, Justin A et al. (2012) Nucleosome stability dramatically impacts the targeting of somatic hypermutation. Mol Cell Biol 32:2030-40
North, Justin A; Javaid, Sarah; Ferdinand, Michelle B et al. (2011) Phosphorylation of histone H3(T118) alters nucleosome dynamics and remodeling. Nucleic Acids Res 39:6465-74
Forties, Robert A; North, Justin A; Javaid, Sarah et al. (2011) A quantitative model of nucleosome dynamics. Nucleic Acids Res 39:8306-13

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