RNF168 binds and amplifies ubiquitin conjugates on damaged chromosomes to allow accumulation of repair proteins.
Authors: Doil C, Mailand N, Bekker-Jensen S, Menard P, Larsen DH, Pepperkok R, Ellenberg J, Panier S, Durocher D, Bartek J, Lukas J, Lukas C.
CellNetworks People: Pepperkok Rainer, Ellenberg Jan
Journal: Cell. 2009 Feb 6;136(3):435-46.

DNA double-strand breaks (DSBs) not only interrupt the genetic information, but also disrupt the chromatin structure, and both impairments require repair mechanisms to ensure genome integrity. We showed previously that RNF8-mediated chromatin ubiquitylation protects genome integrity by promoting the accumulation of repair factors at DSBs. Here, we provide evidence that, while RNF8 is necessary to trigger the DSB-associated ubiquitylations, it is not sufficient to sustain conjugated ubiquitin in this compartment. We identified RNF168 as a novel chromatin-associated ubiquitin ligase with an ability to bind ubiquitin. We show that RNF168 interacts with ubiquitylated H2A, assembles at DSBs in an RNF8-dependent manner, and, by targeting H2A and H2AX, amplifies local concentration of lysine 63-linked ubiquitin conjugates to the threshold required for retention of 53BP1 and BRCA1. Thus, RNF168 defines a new pathway involving sequential ubiquitylations on damaged chromosomes and uncovers a functional cooperation between E3 ligases in genome maintenance.