UVSSA facilitates transcription-coupled repair of DNA interstrand crosslinks.

DNA interstrand crosslinks (ICLs) are covalent bonds between bases on opposing strands of the DNA helix which prevent DNA melting and subsequent DNA replication or RNA transcription. Here, we show that Ultraviolet Stimulated Scaffold Protein A (UVSSA) is critical for ICL repair in human cells, at least in part via the transcription coupled ICL repair (TC-ICR) pathway. Inactivation of UVSSA sensitizes human cells to ICL-inducing drugs, and delays ICL repair. UVSSA is required for replication-independent repair of a single ICL in a fluorescence-based reporter assay. UVSSA localizes to chromatin following ICL damage, and interacts with transcribing Pol II, CSA, CSB, and TFIIH. Specifically, UVSSA interaction with TFIIH is required for ICL repair and transcription inhibition blocks localization of transcription coupled repair factors to ICL damaged chromatin. Finally, UVSSA expression positively correlates with ICL-based chemotherapy resistance in human cancer cell lines. Our data strongly suggest that UVSSA is a novel ICL repair factor functioning in TC-ICR. These results provide further evidence that TC-ICR is a bona fide ICL repair mechanism that contributes to crosslinker drug resistance independently of replication-coupled ICL repair. [Display omitted] • UVSSA is required for cell survival following exposure to crosslink inducing agents. • Loss of UVSSA prevents repair of ICLs in a replica@on-idependent reporter assay. • UVSSA interacts with CSA, CSB, and TFIIH following ICL damage. • UVSSA is central to assembly of transcrip@on coupled ICL repair complex. • UVSSA expression correlates with crosslinker resistance in cancer lines. [ABSTRACT FROM AUTHOR]