DNA damage checkpoint and repair centers.

In eukaryotes, recombinational repair is choreographed by multiprotein complexes that are organized into focal assemblies. These foci are highly dynamic giga-dalton structures capable of simultaneously repairing multiple DNA lesions. Moreover, the composition of these repair centers depends on the nature of the DNA lesion and is tightly coordinated with progression of the cell cycle. Components of DNA repair centers are regulated by post-translational modifications such as phosphorylation, ubiquitination and sumoylation. Repair foci progress through four distinct stages: first, DNA damage recognition and binding of DNA ends by the Mre11 complex and Ku70/80; second, end-processing and binding of single-stranded DNA by replication protein A, which recruits checkpoint proteins; third, recombinational repair during S and G(2) phase; and fourth, disassembly of foci and resumption of the cell cycle.