How ubiquitylation of multiple substrates, including repair proteins and histones, is regulated during nucleotide excision repair (NER) has been unclear. Gracheva et al. show that the histone H2A-ubiquitin binding factor ZRF1 is essential in NER as it mediates remodeling of the novel ubiquitin E3 complex responsible for monoubiquitylation of histone H2A at DNA lesion sites.

Repair of damaged DNA relies on the recruitment of DNA repair factors in a well orchestrated manner. As a prerequisite, the chromatin needs to be decondensed by chromatin remodelers to allow for binding of repair factors and for DNA repair to occur. Recent studies have implicated members of the SWI/SNF and INO80 families as well as PARP1 in nucleotide excision repair (NER). In this study, we report that the endonuclease DICER is implicated in chromatin decondensation during NER. In response to UV irradiation, DICER is recruited to chromatin in a ZRF1-mediated manner. The H2A–ubiquitin binding protein ZRF1 and DICER together impact on the chromatin conformation via PARP1. Moreover, DICER-mediated chromatin decondensation is independent of its catalytic activity. Taken together, we describe a novel function of DICER at chromatin and its interaction with the ubiquitin signalling cascade during GG-NER.

The endoribonuclease DICER facilitates chromatin decondensation during lesion recognition following UV exposure. Chitale and Richly show that DICER mediates the recruitment of the methyltransferase MMSET, which catalyzes the dimethylation of histone H4 at lysine 20 and facilitates the recruitment of the nucleotide excision repair factor XPA.