Siesta-RING1 complexes are variant Polycomb-related ubiquitin ligase complexes that contain the PCGF-family protein Siesta (sist) and RING1 (Sce) contribute to H2AK118 monoubiquitylation outside canonical Polycomb response element-associated regions. The BCORL-SIESTA-RING1 Complex is similar to mammalian PCGF1-type variant PRC1, containing a BCOR-like subunit. (Adapted from FBrf0254426.)