EZH2 is the catalytic subunit of the PRC2 (Polycomb Repressive Complex 2), mediating histone H3 methylation at lysines 9 and 27 (H3K9me and H3K27me) to drive transcriptional repression 1. EZH2 catalyzes mono-, di-, and trimethylation of H3K27, with preference for less-methylated substrates (H3K27me0 > H3K27me1 > H3K27me2) 23. In embryonic stem cells, EZH2-containing PRC2 complexes predominantly generate H3K27me3, essential for stem cell identity and differentiation 4. Beyond canonical histone methylation, EZH2 exhibits non-canonical functions, including binding c-Myc at non-PRC2 targets via a cryptic transactivation domain to activate genes in acute leukemias 5. EZH2 overexpression correlates with poor prognosis across multiple cancersβtriple-negative breast cancer, ovarian cancer, and glioblastomaβand promotes metastasis and therapeutic resistance 6789. In immune contexts, T cell EZH2 drives atherosclerosis by suppressing anti-inflammatory responses and Il-4 expression 10. EZH2 also regulates ferroptosis in kidney injury by suppressing SLC7A11 through H3K27me3 deposition 11. Both catalytic inhibitors and PROTAC-based EZH2 degraders represent therapeutic strategies for EZH2-dependent malignancies.