SCML2 encodes a germline-specific Polycomb group protein that plays critical roles in spermatogenesis and chrX regulation. The protein functions as a key regulator of heterochromatin organization during male germ cell development, where it accumulates on pericentromeric heterochromatin and suppresses PRC1-mediated H2A ubiquitination while promoting H3K27 methylation 1. SCML2 cooperates with RNF8 to regulate histone modifications during meiosis, specifically deubiquitinating H2AK119ub to establish active chrX marks like H3K27 acetylation necessary for sex chromosome X activation 2. The protein contains a unique DNA-binding domain called SCML2 DNA-binding (SDB) repeats that evolved rapidly in rodents and enables chrX binding, particularly to hypomethylated regions 3. Structurally, SCML2 possesses a conserved SLED domain that adopts a novel α/β fold and binds double-stranded DNA in a sequence-specific manner 4. Clinically, SCML2 variants have been identified in patients with primary male infertility, highlighting its importance for reproductive function 5. Additionally, SCML2 interacts with YAP1 in response to androgen signaling and is aberrantly expressed in hepatocellular carcinoma, where it promotes tumor progression through Wnt/β-catenin signaling 67.