DDB2 Complex-Mediated Ubiquitylation around DNA Damage Is Oppositely Regulated by XPC and Ku and Contributes to the Recruitment of XPA

Abstract

UV-damaged-DNA-binding protein (UV-DDB) is a heterodimer comprised of DDB1 and DDB2 and integrated in a complex that includes a ubiquitin ligase component, cullin 4A, and Roc1. Here we show that the ubiquitin ligase activity of the DDB2 complex is required for efficient global genome nucleotide excision repair (GG-NER) in chromatin. Mutant DDB2 proteins derived from xeroderma pigmentosum group E patients are not able to mediate ubiquitylation around damaged sites in chromatin. We also found that CSN, a negative regulator of cullin-based ubiquitin ligases, dissociates from the DDB2 complex when the complex binds to damaged DNA and that XPC and Ku oppositely regulate the ubiquitin ligase activity, especially around damaged sites. Furthermore, the DDB2 complex-mediated ubiquitylation plays a role in recruiting XPA to damaged sites. These findings shed some light on the early stages of GG-NER.