ausblenden:
Schlagwörter:
Cell Line
Chromosomes/*metabolism
*DNA Breaks, Double-Stranded
*DNA Repair
DNA-Binding Proteins/metabolism
Gene Knockdown Techniques
Histones/metabolism
Humans
Intracellular Signaling Peptides and Proteins/metabolism
Protein Structure, Tertiary
Tumor Suppressor p53-Binding Protein 1
Ubiquitin/*metabolism
Ubiquitin-Protein Ligases/chemistry/genetics/*metabolism
Zusammenfassung:
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.
