Seems to be involved in transcriptional silencing in heterochromatin-like complexes. Recognizes and binds histone H3 tails methylated at 'Lys-9', leading to epigenetic repression. May contribute to the association of the heterochromatin with the inner nuclear membrane through its interaction with lamin B receptor (LBR). Involved in the formation of functional kinetochore through interaction with MIS12 complex proteins. Contributes to the conversion of local chromatin to a heterochromatin-like repressive state through H3 'Lys-9' trimethylation, mediates the recruitment of the methyltransferases SUV39H1 and/or SUV39H2 by the PER complex to the E-box elements of the circadian target genes such as PER2 itself or PER1. Mediates the recruitment of NIPBL to sites of DNA damage at double-strand breaks (DSBs) (PubMed:28167679). Binds directly to CHAF1A. Interacts with histone H3 methylated at 'Lys-9' (PubMed:11242053). Part of the E2F6.com-1 complex in G0 phase composed of E2F6, MGA, MAX, TFDP1, CBX3, BAT8, EUHMTASE1, RING1, RNF2, MBLR, L3MBTL2 and YAF2. Interacts with INCENP, TRIM28/TIF1B, KMT5B, KMT5C and SP100 (PubMed:10330177, PubMed:12004135, PubMed:9636146). Interacts with TIF1A (By similarity). Interacts with MIS12 and DSN1 (PubMed:15502821). Can interact directly with CBX5 via the chromoshadow domain (PubMed:9169472). Interacts with POGZ (PubMed:20850016, PubMed:20562864). Interacts with CHAMP1 (PubMed:20850016). The large PER complex involved in the histone methylation is composed of at least PER2, CBX3, TRIM28, SUV39H1 and/or SUV39H2; CBX3 mediates the formation of the complex. Interacts with INCENP (PubMed:9864353, PubMed:21346195). Interacts with NIPBL (via PxVxL motif) (PubMed:28167679). Interacts with LRIF1 (via PxVxL motif) (PubMed:23542155). Interacts with TTLL12 (PubMed:23251473). Interacts with ZNF263; recruited to the SIX3 promoter along with other proteins involved in chromatin modification and transcriptional corepression where it contributes to transcriptional repression (PubMed:32051553). Associates with euchromatin and is largely excluded from constitutive heterochromatin. May be associated with microtubules and mitotic poles during mitosis (Potential). Phosphorylated by PIM1. Phosphorylated during interphase and possibly hyper-phosphorylated during mitosis. Was previously reported to interact with ASXL1. However, this publication has been retracted.