Heterochromatin Protein 1 (HP1, Su(var)205) was first discovered in Drosophila as a dominant suppressor of position-effect variegation and a major component of heterochromatin. Members of the HP1 family are characterised by the presence of an N-terminal chromodomain and a C-terminal chromoshadow domain. In addition to heterochromatin packaging and silencing, HP1 proteins have diverse roles in the nucleus, including the regulation of euchromatic genes. (Adapted from FBrf0193304).