Enables single-stranded RNA binding activity and ubiquitin-protein transferase activator activity. Acts upstream of or within histone ubiquitination and regulation of catalytic activity. Located in heterochromatin and nucleus. Part of PcG protein complex and ubiquitin ligase complex. Is expressed in several structures, including brain. Orthologous to human CBX8 (chromobox 8). [provided by Alliance of Genome Resources, Apr 2022]