The heterochromatin protein 1 (HP1) family, which consists of three isoforms HP1 (CBX5), HP1 (CBX1), and HP1 (CBX3) are chromatin-associated proteins involved in gene regulation and heterochromatin formation.1 CBX proteins have an N-terminal chromodomain, a C-terminal chromoshadow domain (CSD), and a hinge domain which connects the two.2 Extensive post-translational modifications have been observed and mapped on the CBX proteins.3 The chromodomain of CBX1 has been shown to recognize di- and tri-methylated lysine 9 on histone H3 (H3K9me2 and H3K9me3), with a preference for H3K9me3. Binding of CBX1 to methylated histones lEAds to gene silencing and heterochromatin formation.1,4 The CSD region of CBX1 is responsible for homodimerization and interaction with a number of non-histone chromatin-associated proteins, including the BRCA2-interacting protein EMSY, which may be involved in the development of brEAst and ovarian cancer.5,6,7 CBX1 also helps to reorganize chromatin as part of the DNA damage response systems by binding to sites of DNA damage through the CSD region.8,9 Technical Information Synonyms Chromobox Protein Homolog 1 Heterochromatin Protein 1 Homolog Heterochromatin Protein p25 HP1- HP1Hs- M31 Modifier 1 Protein p25 Purity 95% Source recombinant N-terminal GST-tagged protein expressed in E. coli MW 48.9 kDa Formulation 50 mM Tris-HCl, pH 8.0, containing 150 mM sodium chloride and 20% glycerol UniProt Accession P83916