CBX5, also known as Chromobox protein homolog 5, is a regulatory protein belonging to the Polycomb group proteins family with two chromo domains. CBX5 associates with chromosomes during mitosis, specifically with chromatin during metaphase and anaphase. A component of the centromeric and pericentromeric heterochromatin, CBX5 may interact with lamin B receptor (LBR) to contribute to the association of the heterochromatin with the inner nuclear membrane. CBX5 recognizes and binds histone H3 tails methylated at 'Lys-9', leading to epigenetic repression. This methyl-lysine binding protein localized at heterochromatin sites is also known to mediate gene silencing and is involved in the formation of functional kinetochore through interaction with MIS12 complex proteins.