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. They probably act via the methylation of histones, rendering chromatin heritably changed in its expressibility. Scm associates with the PRC1 core complex containing PSC, PC, PH and Sce/RING1. Forms homotypic and heterotypic interactions. Interacts with the SAM domain of ph-p via its SAM domain in vitro. Interacts with corto in vitro. Expressed both maternally and zygotically. Levels are highest in 0-2 hours embryos and at lower levels during later embryonic and larval stages. A modest increase in expression is seen during the pupal stage. Expressed throughout the 9 hours embryo. After 12 hours expression is concentrated in the central nervous system. The SAM domain is essential for function. Belongs to the SCM family.