Yumei Li1, Shanshan Ai1, Xianhong Yu2, Chen Li1, Xin Li1, Yanzhu Yue1, Yusheng Wei3, Chuan-Yun Li1, Aibin He1,2. 1. From the Institute of Molecular Medicine, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking University, China (Y.L., S.A., C.L., X.L., Y.Y., C.-Y.L., A.H.). 2. Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China (X.Y., A.H.). 3. College of Life Science, Peking University, Beijing, China (Y.W.).
Abstract
RATIONALE: Replication-independent histone turnover has been linked to cis-regulatory chromatin domains in cultured cell lines, but its molecular underpinnings and functional relevance in adult mammalian tissues remain yet to be defined. OBJECTIVE: We investigated regulatory functions of replication-independent histone turnover in chromatin states of postmitotic cardiomyocytes from adult mouse heart. METHODS AND RESULTS: We used H2B-GFP (histone 2B-green fluorescent protein) fusion protein pulse-and-chase approaches to measure histone turnover rate in mouse cardiomyocytes. Surprisingly, we found that the short histone half-life (≈2 weeks) contrasted dramatically with the long lifetime of cardiomyocytes, and rapid histone turnover regions corresponded to cis-regulatory domains of heart genes. Interestingly, recruitment of chromatin modifiers, including Polycomb EED (embryonic ectoderm development), was positively correlated with histone turnover rate at enhancers. Mechanistically, through directly interacting with and engaging the BAF (BRG1 [Brahma-related gene-1]-associated factor) complex for nucleosome exchange for stereotyped histone modifications from the free histone pool, EED augmented histone turnover to restrain enhancer overactivation. CONCLUSIONS: We propose a model in which replication-independent histone turnover reinforces robustness of local chromatin states for adult tissue homeostasis.
RATIONALE: Replication-independent histone turnover has been linked to cis-regulatory chromatin domains in cultured cell lines, but its molecular underpinnings and functional relevance in adult mammalian tissues remain yet to be defined. OBJECTIVE: We investigated regulatory functions of replication-independent histone turnover in chromatin states of postmitotic cardiomyocytes from adult mouse heart. METHODS AND RESULTS: We used H2B-GFP (histone 2B-green fluorescent protein) fusion protein pulse-and-chase approaches to measure histone turnover rate in mouse cardiomyocytes. Surprisingly, we found that the short histone half-life (≈2 weeks) contrasted dramatically with the long lifetime of cardiomyocytes, and rapid histone turnover regions corresponded to cis-regulatory domains of heart genes. Interestingly, recruitment of chromatin modifiers, including Polycomb EED (embryonic ectoderm development), was positively correlated with histone turnover rate at enhancers. Mechanistically, through directly interacting with and engaging the BAF (BRG1 [Brahma-related gene-1]-associated factor) complex for nucleosome exchange for stereotyped histone modifications from the free histone pool, EED augmented histone turnover to restrain enhancer overactivation. CONCLUSIONS: We propose a model in which replication-independent histone turnover reinforces robustness of local chromatin states for adult tissue homeostasis.