Polycomb group (PcG) protein. PcG proteins act by forming multiprotein complexes, which are required to maintain the transcriptionally repressive state of homeotic genes throughout development. PcG proteins are not required to initiate repression, but to maintain it during later stages of development. Also required to repress expression of other genes and for localization of sor-1. Binds RNA. Homodimer. Interacts with ubc-9. Binds through its N-terminal region to the N-terminal region of sor-1. Forms subnuclear bodies. Widely expressed. Weakly expressed in most somatic cells of 50-cell stage embryos. At 200 cell stage, it is strongly expressed. By comma stage, it is expressed in most somatic cells. The RNA-binding region is essential for the localization to subnuclear bodies and its function. The SAM-like domain, although only slightly related to the SAM domain, apparently displays a similar function. It is essential for homodimerization, the interaction with ubc-9, and the formation of subnuclear bodies. Sumoylated by ubc-9. Sumoylation is required for the transcriptional regulation of homeotic genes.