Interaction between Chromatin Modifying Complexes and Cohesin (2024)
Undergraduate: June Arricastres
Faculty Advisor: Jill Dowen
Department: Biochemistry and Biophysics
Dysregulation of chromatin organization results in an array of developmental diseases and multiple different forms of cancer. Three-dimensional genome organization is primarily mediated by the cohesin complex and cohesin-interacting proteins to form both transcriptional neighborhoods through CTCF-cohesin interactions and enhancer-promoter loops through unknown mechanisms. Cohesin is a pleiotropic regulator of the genome and there is limited understanding of how cohesin-interacting proteins may regulate cohesin function. A comprehensive cohesin interactome has not been defined and may be key for understanding the molecular mechanisms by which cohesin regulates chromosome structure and gene expression. We utilized the TurboID biotin proximity labeling method to establish a cohesin interactome. Within the cohesin interactome, an interaction between cohesin and chromatin modifying complexes (CMCs) was revealed, including the SWI/SNF, ISWI, NuRD, MLL, NuA4, Polycomb Group (PcG), and Sin3A complexes. Nearly all the interactions detected by TurboID-Mass Spec that were selected for validation by co-immunoprecipitation and western blot were confirmed. This finding suggests potential crosstalk between the histone-mediated chromatin landscape and cohesin-mediated 3D genome organization via physical interactions. To assess the role of chromatin modifying complexes in cohesin regulation of the genome, the stability of the cohesin-SWI/SNF complex interaction was investigated. Mouse embryonic stem cells (mESCs) harboring a cohesin cancer mutation (SMC1AR586W) exhibited reduced cohesin localization to enhancer and promoter regions, but unchanged cohesin levels at CTCF genomic sites. This mutation did not affect the interaction of SWI/SNF and cohesin, despite reduced cohesin localization at enhancer and promoter regions. The decreased localization of cohesin coupled with maintained interaction of cohesin-SWI/SNF may indicate that cohesin mutations may cause an alteration of the stability of chromatin modifying complexes on the genome, contributing to the development of disease.