Differential oligomerization regulates PHF13 chromatin function and affinity [ATAC-seq]

PHF13 is a H3K4me3 epigenetic reader, that modulates key chromatin processes including transcription, DNA damage response and chromatin architecture. PHF13 is found aberrantly regulated in different cancers and its misexpression alters the epigenetic landscape of key transcription factors that regulate Epithelial to Mesenchymal transition. In this study we sought to understand how PHF13’s chromatin affinity and diverse chromatin functions are intrinsically regulated. Our results show that PHF13 can oligomerize via conserved ordered regions in its N- and C- terminus increasing its chromatin valence and avidity. Impressively, a 4-fold over expression of PHF13 was sufficient to globally compact chromatin, dependent on its ordered dimerizing regions and oligomerization potential. Unexpectedly, we discovered that PHF13 can self-associate independent of its ordered domains via intrinsically disordered regions, which conversely reduced PHF13’s chromatin affinity. Our findings support that there is an intrinsic balance between PHF13’s ordered and disordered regions that regulates PHF13 chromatin affinity, and suggest that PHF13 can phase transition between polymer-polymer and liquid-liquid phase separation states to impact chromatin structure and function. U2OS cells were transfected and cultured with various constructs to overexpress PHF13 and its mutant variants. ATAC-seq were performed to assess aceability changes to identify PHF13 mutants that induce protein condensation versus gene condensation.