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, 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 CBX5 has been shown to recognize di- and tri-methylated lysine 9 on histone H3 (H3K9me2 and H3K9me3), with a preference for H3K9me3. Binding of CBX5 to methylated histones lEAds to gene silencing and heterochromatin formation.1,4 H3K9 trimethylation by the methyltransferase SETDB1 crEAtes a binding site for recruitment of CBX5, lEAding to chromatin condensation and gene silencing.5 The chromoshadow domain facilitates protein-protein interactions like homodimerization and recruitment of nuclEAr proteins involved in transcriptional regulation.6 The chromoshadow domain is also responsible for recruitment to sites of DNA damage, where CBX5 helps to reorganize chromatin as part of the DNA damage response system.7 Technical Information Synonyms Antigen p25 Chromobox Protein Homolog 5 Heterochromatin Protein 1- HP1- Purity 95% Source recombinant N-terminal His-tagged protein expressed in E. coli MW 24.1 kDa Formulation 50 mM Tris-HCl, pH 8.0, containing 150 mM sodium chloride and 20% glycerol UniProt Accession P45973