Recruitment of heterochromatin protein 1 to DNA repair sites.

Heterochromatin protein 1 (HP1) was originally identified as a constitutive component of heterochromatin. However it is recognized now that it plays an important role in a number of dynamic processes in the cell nucleus, including transcriptional repression and regulation of euchromatic genes. Recent reports demonstrate that HP1 may be involved in the DNA damage response. Two seemingly contradictory phenomena have been observed-HP1 detachment from chromatin and HP1 recruitment to damaged DNA foci. Based on quantitative FRAP and FLIP studies carefully designed to minimize phototoxicity, we demonstrate that HP1 is recruited to the damaged regions in hetero- as well as euchromatin within a few minutes after damage. 2009 International Society for Advancement of Cytometry.