phosphorylated Heterochromatin protein HP1α, delta CSD b4 mutant

The heterochromatin protein HP1α consists of an N-terminal disordered phosphorylation tail (N-tail), chromodomain (CD), central flexible hinge region (HR), and C-terminal chromo shadow domain (CSD). CD binds to the lysine9-trimethylated histone H3 (H3K9me3) tail in nucleosomes and CSD forms a dimer bridging two nucleosomes with H3K9me3. Therefore, the CSD deletion mutant of HP1α shows the monomer. HP1α has four successive serine residues in N-tail that are phosphorylated by CK2 in vivo. In the pΔCSD b4 mutant, 68 to 72 basic residues are replaced with Ala.