Antigen p25, HP1-_, CBX5, CBX5_HUMAN, Chromobox homolog 5 (HP1 alpha homolog, Drosophila), Chromobox homolog 5, Chromobox protein homolog 5, Heterochromatin protein 1 alpha, Heterochromatin protein 1, Heterochromatin protein 1 homolog alpha, HP1 alpha, HP1 alpha homolog, HP1, HP1A, HP1Hs alpha.
Component of heterochromatin that recognizes and binds histone H3 tails methylated at Lys-9 (H3K9me), leading to epigenetic repression. In contrast, it is excluded from chromatin when Tyr-41 of histone H3 is phosphorylated (H3Y41ph). Can interact with lamin-B receptor (LBR). This interaction can contribute to the association of the heterochromatin with the inner nuclear membrane. Involved in the formation of functional kinetochore through interaction with MIS12 complex proteins.