Heterochromatin protein 1 (HP1) (HP1)

Heterochromatin protein 1 (HP1) is a family of highly conserved non-histone chromosomal proteins essential for the structural organization of the nucleus and the regulation of gene expression. In humans, the family includes three isoforms—HP1α (CBX5), HP1β (CBX1), and HP1γ (CBX3)—which function as epigenetic "readers" by binding to trimethylated lysine 9 of histone H3 (H3K9me3) through their N-terminal chromodomain. This interaction promotes the formation of repressive heterochromatin, leading to transcriptional silencing of specific genomic regions. Beyond gene repression, HP1 proteins are involved in critical cellular processes including DNA damage repair, chromosome segregation during mitosis, and the maintenance of telomere integrity. Dysregulation of HP1 expression is linked to various pathologies, particularly cancer, where it can influence tumor progression, metastasis, and resistance to therapy. As a result, HP1 is being investigated as a therapeutic target, with experimental small molecules designed to disrupt its binding to methylated histones to modulate the epigenetic landscape in disease states.

Other names

Chromobox protein homologCBXHP1 alphaHP1 betaHP1 gammaAntigen p25Heterochromatin protein 1 homolog alphaHeterochromatin protein 1 homolog betaHeterochromatin protein 1 homolog gamma

Inhibition of the interaction between the HP1 chromodomain and trimethylated histone H3 lysine 9 (H3K9me3)