EZH1

EZH1 is a PRC2 catalytic homolog that methylates histone H3 lysine 27 and supports transcriptional repression in chromatin regulation[1]. Mechanistically, EZH1 colocalizes with H3K27me3 and preserves this mark on development-related genes when EZH2 is absent, linking EZH1 to embryonic stem cell identity and pluripotency execution[1]. In adult models, EZH1 maintains hematopoietic stem cells in a slow-cycling, undifferentiated state and protects them from senescence-like cell-cycle arrest[2]. Compared with EZH2, EZH1 forms similar PRC2 complexes but represses chromatin through a distinct mechanism, because PRC2-EZH2 strongly catalyzes H3K27me2/3 whereas PRC2-EZH1 more directly compacts chromatin[3]. Functional redundancy is context-dependent, as EZH1 and EZH2 jointly sustain H3K27 trimethylation in mouse skin, where double targeting abolishes H3K27me3 and disrupts hair follicle homeostasis and wound repair[4]. In cancer research, EZH1/2 dual inhibitors provide experimental tools to test whether simultaneous EZH1 and EZH2 blockade suppresses H3K27me3 more effectively than EZH2-selective inhibition[5]. Valemetostat studies further support EZH1/2 inhibition as a translational model in relapsed or refractory adult T-cell leukemia/lymphoma[6].