A H3K14ub-Driven Heterochromatin Formation and Stable Inheritance Pathway

HUANG Yuanyong^1,2,3*, QI Hongyun⁴, CHEN Degui⁴, WONG Jiemin^1,2,3*

(¹Wuhu Hospital, East China Normal University (the Second People’s Hospital, Wuhu), Wuhu 241000, China; ²Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, Shanghai 200241, China; ³Joint Center for Translational Medicine, Fengxian District Central Hospital, Shanghai 201499, China; ⁴Shanghai Key Laboratory of Molecular Andrology, Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai 200031, China)

Abstract:

Maintaining proper and stable compartmentalization of eukaryotic genome into heterochromatin and euchromatin during mitosis, along with heterochromatin proper reassembly, maintenance and inheritance, are of critical biological significance for centromere assembly, sister chromatid cohesion and separation, genomic integrity and stability, and transcriptional regulation. Heterochromatin instability increases the risk of cancer, aging and related diseases, neurodegenerative disorders. Previous studies suggest a self-templating pathway involving “read-write” of H3K9 methylation by methyltransferase SUV39H as the core mechanism for heterochromatin reassembly, maintenance and inheritance during mitosis. This study reveals that the “read-write” of H3K9 methylation by SUV39H in mammalian cells is insufficient to achieve stable inheritance of pericentromeric heterochromatin during mitosis, requiring additional assistance from H3K14 ubiquitination. Researchers identified G2E3 as an H3K14ub-specific, pericentromeric heterochromatin-localized E3 ligase. Importantly, H3K14ub catalyzed by G2E3 during mitosis is essential for SUV39H targeting to pericentromeric heterochromatin and for its methyltransferase activity. Mechanistically, G2E3 is highly expressed during G2/M phase, and RNA-dependently binds to pericentromeric heterochromatin on mitotic chromosomes and catalyzes H3K14ub, which is essential for subsequent sequential SUV39H and HP1 targeting to pericentromeric heterochromatin, facilitating H3K9me3 accumulation and spreading to ensure heterochromatin reassembly and inheritance. Researchers further revealed the chromodomain of SUV39H is a dual reader of H3K14ub and H3K9me3, with H3K14ub binding being primary for pericentromeric localization. Notably, the absence of G2E3 not only severely impairs pericentromeric heterochromatin reassembly but also leads to aberrant accumulation of SUV39H and H3K9me3 in numerous euchromatic regions and a widespread transcriptional repression. Thus, this study reveals H3K14ub-driven H3K9me3 as a conserved mechanism of pericentromeric heterochromatin reassembly, maintenance and inheritance, which is in turn crucial for proper genomic chromatin compartmentalization and transcriptional regulation.

CSTR: 32200.14.cjcb.2026.04.0001