A UV-sensitive syndrome patient with a specific CSA mutation reveals separable roles for CSA in response to UV and oxidative DNA damage

Abstract

UV-sensitive syndrome (UV S S) is a recently-identified autosomal recessive disorder characterized by mild cutaneous symptoms and defective transcription-coupled repair (TC-NER), the subpathway of nucleotide excision repair (NER) that rapidly removes damage that can block progression of the transcription machinery in actively-transcribed regions of DNA. Cockayne syndrome (CS) is another genetic disorder with sun sensitivity and defective TC-NER, caused by mutations in the CSA or CSB genes. The clinical hallmarks of CS include neurological/developmental abnormalities and premature aging. UV S S is genetically heterogeneous, in that it appears in individuals with mutations in CSB or in a still-unidentified gene. We report the identification of a UV S S patient (UV S S1VI) with a novel mutation in the CSA gene (p.trp361cys) that confers hypersensitivity to UV light, but not to inducers of oxidative damage that are notably cytotoxic in cells from CS patients. The defect in UV S S1VI cells is corrected by expression of the WT CSA gene. Expression of the p.trp361cys-mutated CSA cDNA increases the resistance of cells from a CS-A patient to oxidative stress, but does not correct their UV hypersensitivity. These findings imply that some mutations in the CSA gene may interfere with the TC-NERdependent removal of UV-induced damage without affecting its role in the oxidative stress response. The differential sensitivity toward oxidative stress might explain the difference between the range and severity of symptoms in CS and the mild manifestations in UV s S patients that are limited to skin photosensitivity without precocious aging or neurodegeneration.

Mutations in UVSSA cause UV-sensitive syndrome and impair RNA polymerase IIo processing in transcription-coupled nucleotide-excision repair

“…CS but not UV S S cells are sensitive to oxidative-DNA-damage 5,7,29,30 ; this differential sensitivity could explain the difference between symptoms in CS and UV S S. Our findings, however, suggest that aberrant RNA-polIIo may also contribute to the clinical outcome (Supplementary Fig. 15).…”

“…UVSSA interacts with TFIIH, ERCC6, and RNA-polIIo and the VHS-domain is indispensable for TC-NER activity and for ubiquitination and dephosphorylation roles in the processing of stalled RNA-polIIo. We hypothesize that UVSSA directly recruits TFIIH at sites where RNA-polIIo is stalled at UV-damage (but not at oxidative-damage: CS but not UV S S cells are sensitive to oxidative-DNA-damage 5,7,29,30 ; this differential sensitivity could explain the difference between symptoms in CS and UV S S. Our findings, however, suggest that aberrant RNA-polIIo may also contribute to the clinical outcome (Supplementary Fig. 15).…”

“…ERCC8 and ERCC6 genes are responsible for both CS and UV S S 7,8 . To evaluate whether UVSSA mutations may also result in CS-phenotypes, we sequenced the UVSSA gene of 61 CS-patients whose genetic defects had not yet been determined (Supplementary Table 4).…”

Papel das proteínas XPD e DNA polimerase eta nas respostas de células humanas a danos no genoma

“…Os pacientes COFS apresentam mutações em CSB (Meira et al, 2000), XPD (Graham et al, 2001), XPG (Hamel et al, 1996) ou ERCC1 (Jaspers et al, 2007). UVSS é caracterizada somente por fotossensibilidade, sem nenhum outro sintoma de CS, nem aumento na incidência de desenvolvimento de câncer; os pacientes UVSS podem ser mutações em CSA (Nardo et al, 2009), CSB (Horibata et al, 2004) ou UVSSA (Nakazawa et al 2012;Schwertman et al, 2012;Zhang et al, 2012).…”

“…Além do reparo de lesões complexas formadas pelo estresse oxidativo pela via de NER, outra forma de participação de NER no reparo de lesões oxidadas é através do papel regulatório de algumas proteínas de NER sobre proteínas de BER. De fato, já foram descritas interações entre proteínas de NER e diversas glicosilases, como por exemplo XPG e NTH1 (Klungland et al, 1999a), XPC e OGG1 (D'Errico et al, 2006), CSB e NEIL1 (Muftuoglu et al, 2009) e NEIL2 (Aamann et al, 2014) (Berra et al, 2013), assim como células XPA (Berra et al, 2013), CSA e CSB (De Waard et al, 2004;D'Errico et al, 2007;Nardo et al, 2009) e XP-G/CS (Soltys et al, 2013).…”