Histone-binding protein, which is part of various corepressor complexes. Mediates the recruitment of corepressor complexes to target genes, followed by chromatin compaction and repression of transcription. Plays a role during myogenesis: required for the maintenance of undifferentiated states of myogenic progenitor cells via interaction with MYOD1. Interaction with MYOD1 leads to the recruitment of associated corepressors and silencing of MYOD1 target genes. Part of the SLC complex in germ cells, where it may play a role during spermatogenesis. {ECO:0000269|PubMed:17599839, ECO:0000269|PubMed:23349461, ECO:0000269|PubMed:23592795}. This is the function of Ensembl gene identifier ENSG00000163935 (SFMBT1, Scm like with four mbt domains 1).