Beyond Canonical Chromatin: Defining Variant Histone Interactions and Turnover

About This Grant

Project abstract The nucleosome is the fundamental unit of chromatin and functions as a signaling hub in genomic processes that define cell growth and differentiation. Incorporation of histone variants changes the chemical and physical properties of chromatin, leading to distinct protein interactions and altering chromatin functions. Dysregulation of variant histones drives cancer development and progression, neurological disorders, and developmental diseases. Despite their fundamental importance to cellular function and disease, variant histone protein interaction networks remain poorly characterized. Our laboratory addresses this critical knowledge gap by using advanced proteomics to systematically map variant nucleosome interactomes and high-resolution structural biology to elucidate the molecular mechanisms governing these newly identified interactions. We are currently focusing on variant histones H2A.Z, H3.3, and CENP-A that are necessary for maintaining genomic integrity and cellular identity. We have developed an innovative nucleosome reconstitution approach that enables precise control over histone variant composition, paired with cutting-edge quantitative mass spectrometry to dissect variant nucleosome protein interaction networks. Over the next five years, we will determine how different combinations of H2A.Z, H3.3, and CENP-A within nucleosomes generate distinct regulatory signals and recruit specific protein complexes to control diverse nuclear functions. A major focus in our studies involves elucidating CENP-A turnover mechanisms. We are investigating how CENP-A overexpression is controlled through targeted proteasomal degradation during mitosis. Using cryogenic electron microscopy, we will visualize at near atomic resolution how CENP-A is specifically recognized and ubiquitinated by the DCAF11-E3 ubiquitin ligase complex. This work will provide mechanistic insights guiding hypothesis-driven functional studies and informing novel therapeutic approaches for cancers with dysregulated CENP-A levels. Altogether, our research program establishes universal principles governing variant histone recognition and CENP-A turnover in human cells, generating fundamental insights into gene regulation while uncovering practical applications for targeting chromatin alterations in human diseases. In addition, by discovering novel nucleosome interactions it lays the foundation for future studies in my group focusing on human histone homeostasis.