Regulation of transcription elongation by the XPG-TFIIH complex is implicated in Cockayne syndrome
XPGis a causative gene underlying the photosensitive disorder, xeroderma pigmentosum group G, and is involved in nucleotide excision repair. Here, we show that XPG knockdown represses epidermal growth factor (EGF)-inducedFOStranscription at the level of transcription elongation with little effect on EGF signal transduction. XPG interacted with transcription elongation factors in concert with TFIIH, suggesting that the XPG-TFIIH complex serves as a transcription elongation factor. The XPG-TFIIH complex was recruited to promoter and coding regions of both EGF-induced (FOS) and housekeeping (EEF1A1) genes. Further, EGF-induced recruitment of RNA polymerase II and TFIIH toFOSwas reduced by XPG knockdown. Importantly, EGF-inducedFOStranscription was markedly lower in XP-G/CS cells expressing truncated XPG than in control cells expressing wild-type (WT) XPG, with less significant decreases in XP-G cells with XPG nuclease domain mutations. In corroboration of this finding, both WT XPG and a missense XPG mutant from an XP-G patient were recruited toFOSupon EGF stimulation, but an XPG mutant mimicking a C-terminal truncation from an XP-G/CS patient was not. These results suggest that the XPG-TFIIH complex is involved in transcription elongation, and that defects in this association may partly account for Cockayne syndrome in XP-G/CS patients.