May function as transcription repressor; The repressive effects are mediated, at least in part, by recruitment of deacetylase activity. May play a role as negative regulator of postmeiotic genes acting through CBX3 complex formation and centromere association. Can form homodimers and heterodimers. Interacts with CBX5, CBX1 and CBX3 via PxVxL motif. Forms discrete foci within the centromeric chromocenter and surrounding nucleoplasm. Predominant in testis, specifically in elongating spermatids. No significant expression in testis of 2- or 3-week-old mouse, but clear detection at the age of 4 weeks.