Based on limited published evidence, GMCL2 is a probable substrate-specific adapter of an E3 ubiquitin-protein ligase complex mediating ubiquitination and proteasomal degradation of target proteins 1. It possesses cullin family protein binding capacity and localizes to the nucleus. The related paralog GMCL1, but not GMCL2, directly interacts with 53BP1 and functions in mitotic surveillance regulation 2. GMCL2's specific biological role in spermatogenesis and its substrate targets remain largely uncharacterized.