Cells can easily repair damaged DNA. Yet to fix what's broken, the repair machinery must first get to the site of the damage. The problem is that DNA is wound up and compacted with proteins into a fairly inaccessible chromatin structure. A paper in the March issue of Nature Structural Biology reports how the DNA-repair enzyme Rad54 remodels chromatin and pushes repressive nucleosome structures out of the way.
Rad54 is a protein required for the repair of lesions that affect both strands of DNA. Together with other products of the RAD52 group of genes, it helps mediate repair through a DNA recombination event. Rad54 shows sequence similarity to a family of DNA-dependent ATPases involved in the displacement or removal of nucleosomes in chromatin. Steve Kowalczykowski and collaborators (University of California, USA) now show that Rad54 catalyzes the redistribution of nucleosome position by sliding nucleosomes along DNA. Further, the activity of Rad54 is stimulated by a Rad51–ssDNA nucleoprotein filament. This suggests that the 'crowbar' activity of Rad54 may be specific to DNA repair-recombination events, providing the cell with an effective tool for an essential repair job.
Stephen C. Kowalczykowski
Center for Genetics and Development
University of California
Tel: +1 530 752 5938
Also available online.
(C) Nature Structural Biology press release.
Message posted by: Trevor M. D'Souza