Poly(ADP-ribosyl)ated chromatin domains: access granted.

The seemingly static architecture of interphase and mitotic chromatin betrays an otherwise elegantly dynamic entity capable of remodelling itself to facilitate DNA replication, transcription, repair and recombination. Remodelling of local chromatin domains in response to physiological cues proceeds, at least in part, through transient cycles of relaxation and condensation that require use of histone variants and post-translational modifications of histones. Studies have connected poly(ADP-ribosyl)ation of histones with virtually every aspect of DNA metabolism and function over the years, most notably with the response to DNA damage, where convincing evidence supports its essential role granting repair machinery access to damaged DNA. Recent reports extend this notion to transcription and the maintenance of genomic stability, thereby supporting a general role for nuclear poly(ADP-ribosyl)ation in many aspects of genomic activity. The phenomenon might contribute to the 'histone code' by dictating levels of local chromatin compaction.