Function of heterochromatin protein 1 during DNA repair

This review focuses on the function of heterochromatin protein HP1 in response to DNA damage. We specifically outline the regulatory mechanisms in which HP1 and its interacting partners are involved. HP1 protein subtypes (HP1 alpha, HP1 beta, and HP1 gamma) are the main components of constitutive heterochromatin, and HP1 alpha and HP1 beta in particular are responsible for heterochromatin maintenance. The recruitment of these proteins to DNA lesions is also important from the perspective of proper DNA repair mechanisms. For example, HP1 alpha is necessary for the binding of the main DNA damage-related protein 53BP1 at DNA repair foci, which are positive not only for the HP1 alpha protein but also for the RAD51 protein, a component of DNA repair machinery. The HP1 beta protein also appears in monomeric form in DNA lesions together with the evolutionarily well-conserved protein called proliferating cell nuclear antigen (PCNA). The role of HP1 in DNA lesions is also mediated via the Kap1 transcription repressor. Taken together, these results indicate that the function of HP1 after DNA injury depends strongly on the kinetics of other DNA repair-related factors and their post-translational modifications, such as the phosphorylation of Kap-1.