p44/SSL1, the regulatory subunit of the XPD/RAD3 helicase, plays a crucial role in the transcriptional activity of TFIIH.
In order to unravel the mechanism that regulates transcription of protein-coding genes, we investigated the function of the p44 subunit of TFIIH, a basal transcription factor that is also involved in DNA repair. We have shown previously that mutations in the C terminus of the XPD helicase, another subunit of TFIIH, prevent its regulation by p44 (Coin, F., Bergmann, E., Tremeau-Bravard, A., and Egly, J. M. (1999) EMBO 18, 1357-1366). By using a site-directed mutagenesis approach within the p44 region from amino acids 66 to 200, we indicate how a decrease in the interaction between p44 and XPD results in a decrease of the XPD helicase activity and leads to a defect in the first steps of the transcription reaction, namely the first phosphodiester bond formation and promoter clearance. We thus provide some explanation for the transcriptional defect found in SSL1 mutated yeast (Wang, Z., Buratowski, S., Svejstrup, J. Q., Feaver, W. J., Wu, X., Kornberg, R. D., Donahue, T. F., and Friedberg, E. C. (1995) Mol. Cell. Biol. 15, 2288-2293). Moreover, this study shows how the activity of the the cyclin-dependent kinase-activating kinase associated with TFIIH complex in stimulating transcription is mediated in part by p44/XPD interaction.
Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, B.P.163, 67404 Illkirch Cedex, C.U. de Strasbourg, France.
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Seroz
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Bradsher
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D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000502:physiology*; D000595:Amino Acid Sequence; D017124:Conserved Sequence; D004265:DNA Helicases / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D013329:Structure-Activity Relationship; D051758:Transcription Factor TFIIH; D014157:Transcription Factors / Q000502:physiology*; D019473:Transcription Factors, TFII; D014158:Transcription, Genetic
D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D019473:Transcription Factors, TFII; D051758:Transcription Factor TFIIH; D000251:Adenosine Triphosphatases; C061897:Rad3 protein, S cerevisiae; D004265:DNA Helicases