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 TAY-SIESTA-RING1 Complex is similar to mammalian PCGF3/5-type variant PRC1 complexes, containing a subunit encoded by tay, ortholog of human AUTS2. (Adapted from FBrf0254426.)