Dual involvement of TFIIH in DNA repair and transcription

The catrier of genetic information, deoxyribonucleic acid (DNA), appears at the macromolecular level as an extremely stable molecule as it is faithfully duplicated and transmitted from mother to daughter cells. At the molecular level, however, DNA is subject to continuous attack, even under physiological conditions and temperatme (1). Such endogenous damage is mainly due to reactivity of the base moiety and not of the sugat'-phosphate backbone. The main lesions introduced are due to hydrolysis, e.g. of the N-glycosidic bond resulting in abasic sites, oxidation reactions, and non-enzymatic alkylation. In contrast to these modifications, DNA damage can also be induced by environmental factors, such as chemicals that are reactive with base groups, or physical agents, sllch as UV or ionizing radiation. Both spontaneous and induced DNA damage can interfere directly with DNA metabolism and result in abnormal cell behavior, cell death, or inducti

Affinity purification of human DNA repair/transcription factor TFIIH using epitope-tagged xeroderma pigmentosum B protein

TFIIH is a high molecular weight complex with a remarkable dual function in nucleotide excision repair and initiation of RNA polymerase II transcription. Mutations in the largest subunits, the XPB and XPD helicases, are associated with three inherited disorders: xeroderma pigmentosum, Cockayne's syndrome, and trichothiodystrophy. To facilitate the purification and biochemical characterization of this intricate complex, we generated a cell line stably expressing tagged XPB, allowing the

Cloning of a human homolog of the yeast nucleotide excision repair gene MMS19 and interaction with transcription repair factor TFIIH via the XPB and XPD helicases

Nucleotide excision repair (NER) removes UV-induced photoproducts and numerous other DNA lesions in a highly conserved 'cut-and-paste' reaction that involves approximately 25 core components. In addition, several other proteins have been identified which are dispensable for NER in vitro but have an undefined role in vivo and may act at the interface of NER and other cellular processes. An intriguing example is the Saccharomyces cerevisiae Mms19 protein that has an unknown dual function in NER and RNA polymerase II transcription. Here we report the cloning and characterization of a human homolog, designated hMMS19, that encodes a 1030 amino acid protein with 26% identity and 51% similarity to S.cerevisiae Mms19p and with a strikingly similar size. The expression profile and nuclear location are consistent with a repair function. Co-immunoprecipitation experiments revealed that hMMS19 directly interacts with the XPB and XPD subunits of NER-transcription factor TFIIH. These findings extend the conservation of the NER apparatus and the link between NER and basal transcription and suggest that hMMS19 exerts its function in repair and transcription by interacting with the XPB and XPD he