chromo shadow domain of heterochromatin protein 1 homolog beta
heterochromatin protein 1 homolog beta (also known as HP1beta, Cbx1, chromobox 1) is a highly conserved non-histone protein, which is a member of the heterochromatin protein family, and is enriched in the heterochromatin and associated with centromeres. HP1beta has a single N-terminal chromodomain which can bind to histone proteins via methylated lysine residues, and a C-terminal chromo shadow domain (CSD) which is responsible for the homodimerization and interaction with a number of chromatin-associated non-histone proteins; a flexible hinge region separates the CD and CSD and may bind nucleic acid. HP1beta may play an important role in the epigenetic control of chromatin structure and gene expression. CSD domains have only been found in proteins that also possess a related chromodomain, while chromodomains can exist in isolation. HP1 is a highly conserved non-histone chromosomal protein that is evolutionarily conserved from fission yeast to plants and animals. The HP1 CSD, in addition to interacting with various proteins bearing the PXVXL motif, also interacts with a region of histone H3 that bears the similar PXXVXL motif. There are three human homologs of HP1 proteins: HP1alpha (also known as Cbx5), HP1beta, and HP1gamma (also known as Cbx3). The CSD domains of all three human HP1 homologs have similar affinities to the PXXVXL motif of histone H3
Jiyao W et al.(2023). "The conserved domain database in 2023.",