Key points are not available for this paper at this time.
The RNA polymerase II general transcription factor TFIIH is composed of 9 known subunits and possesses DNA helicase and protein kinase activities. The kinase subunits of TFIIH in animal cells, Cdk7, cyclin H, and MAT1, were independently isolated as an activity termed CAK (Cdk-activating kinase), which phosphorylates and activates cell cycle kinases. However, CAK activity of TFIIH subunits could not be demonstrated in budding yeast. TFB3, the 38-kDa subunit of yeast TFIIH, is the homolog of mammalian MAT1. By random mutagenesis we have isolated a temperature-sensitive mutation in the conserved RING domain. The mutant Tfb3 protein associates less efficiently with the kinase moiety of TFIIH than the wild type protein. In contrast to lethal mutants in other subunits of TFIIH, this mutation does not impair general transcription. Transcription ofCLB2, and possibly other genes, is reduced in the mutant. At the restrictive temperature, the cells display a defect in cell cycle progression, which is manifest at more than one phase of the cycle. To conclude, in the present study we bring another demonstration of the multifunctional nature of TFIIH. The RNA polymerase II general transcription factor TFIIH is composed of 9 known subunits and possesses DNA helicase and protein kinase activities. The kinase subunits of TFIIH in animal cells, Cdk7, cyclin H, and MAT1, were independently isolated as an activity termed CAK (Cdk-activating kinase), which phosphorylates and activates cell cycle kinases. However, CAK activity of TFIIH subunits could not be demonstrated in budding yeast. TFB3, the 38-kDa subunit of yeast TFIIH, is the homolog of mammalian MAT1. By random mutagenesis we have isolated a temperature-sensitive mutation in the conserved RING domain. The mutant Tfb3 protein associates less efficiently with the kinase moiety of TFIIH than the wild type protein. In contrast to lethal mutants in other subunits of TFIIH, this mutation does not impair general transcription. Transcription ofCLB2, and possibly other genes, is reduced in the mutant. At the restrictive temperature, the cells display a defect in cell cycle progression, which is manifest at more than one phase of the cycle. To conclude, in the present study we bring another demonstration of the multifunctional nature of TFIIH. Cdk-activating kinase hemagglutinin 5-fluoroorotic acid open reading frame hydroxyurea cyclin-dependent kinase C-terminal domain The set of proteins required for regulated transcription of eukaryotic mRNAs includes in addition to RNA polymerase II the general transcription factors (TFIIA, TFIIB, TFIID, TFIIE, TFIIF, TFIIH) (Refs. 1Lemon B. Tjian R. Genes Dev. 2000; 14: 2551-2569Crossref PubMed Scopus (606) Google Scholar, 2Buratowski S. Curr. Opin. Cell Biol. 2000; 12: 320-325Crossref PubMed Scopus (19) Google Scholar, 3Hampsey M. Microbiol. Mol. Biol. Rev. 1998; 62: 465-503Crossref PubMed Google Scholar and references therein) as well as proteins involved in transducing regulatory influences on the general machinery (1Lemon B. Tjian R. Genes Dev. 2000; 14: 2551-2569Crossref PubMed Scopus (606) Google Scholar, 2Buratowski S. Curr. Opin. Cell Biol. 2000; 12: 320-325Crossref PubMed Scopus (19) Google Scholar, 4Lee T.I. Young R.A. Annu. Rev. Genet. 2000; 34: 77-137Crossref PubMed Scopus (632) Google Scholar) and modulating chromatin structure (4Lee T.I. Young R.A. Annu. Rev. Genet. 2000; 34: 77-137Crossref PubMed Scopus (632) Google Scholar, 5Wu J. Grunstein M. Trends Biochem. Sci. 2000; 25: 619-623Abstract Full Text Full Text PDF PubMed Scopus (315) Google Scholar, 6Jenuwein T. Allis C.D. Science. 2001; 293: 1074-1080Crossref PubMed Scopus (7708) Google Scholar). Individual components have unique roles in the process of transcription. For example, TFIIH possesses DNA unwinding activity (3Hampsey M. Microbiol. Mol. Biol. Rev. 1998; 62: 465-503Crossref PubMed Google Scholar) and a protein kinase activity directed at the carboxyl terminal domain (CTD) of the largest subunit of RNA polymerase II (3Hampsey M. Microbiol. Mol. Biol. Rev. 1998; 62: 465-503Crossref PubMed Google Scholar). A new perspective on the functions of the transcriptional machinery has emerged with the discovery that TFIIH is a necessary participant in a distinct cellular process: excision repair of DNA damage (reviewed in Refs. 7Svejstrup J.Q. Vichi P. Egly J.M. Trends Biochem. Sci. 1996; 21: 346-350Abstract Full Text PDF PubMed Scopus (196) Google Scholar and 8de Laat W.L. Jaspers N.G. Hoeijmakers J.H. Genes Dev. 1999; 13: 768-785Crossref PubMed Scopus (926) Google Scholar). Thus, components of the transcriptional machinery may be involved in other cellular processes, allowing a possibility of coordinating such processes with transcription. TFIIH is composed of nine known subunits, all of which are conserved between yeast and animal cells. The subunits of yeast TFIIH are encoded by the genes: SSL2, RAD3, TFB1, SSL1,TFB2, TFB3, TFB4, CCL1, andKIN28 (3Hampsey M. Microbiol. Mol. Biol. Rev. 1998; 62: 465-503Crossref PubMed Google Scholar, 7Svejstrup J.Q. Vichi P. Egly J.M. Trends Biochem. Sci. 1996; 21: 346-350Abstract Full Text PDF PubMed Scopus (196) Google Scholar). The Kin28p and Ccl1p subunits of TFIIH are, respectively, the catalytic and cyclin-like subunits of a protein kinase that phosphorylates the CTD of RNA polymerase II (3Hampsey M. Microbiol. Mol. Biol. Rev. 1998; 62: 465-503Crossref PubMed Google Scholar, 7Svejstrup J.Q. Vichi P. Egly J.M. Trends Biochem. Sci. 1996; 21: 346-350Abstract Full Text PDF PubMed Scopus (196) Google Scholar, 9Frit P. Bergmann E. Egly J.M. Biochimie (Paris). 1999; 81: 27-38Crossref PubMed Scopus (55) Google Scholar). The homologs of KIN28 and CCL1 in animal cells are cdk7 and cyclin H (cycH), respectively. Interestingly, cdk7 and cycH have been independently isolated as components of a protein kinase termed CAK1 (CDK-activating kinase) (3Hampsey M. Microbiol. Mol. Biol. Rev. 1998; 62: 465-503Crossref PubMed Google Scholar, 7Svejstrup J.Q. Vichi P. Egly J.M. Trends Biochem. Sci. 1996; 21: 346-350Abstract Full Text PDF PubMed Scopus (196) Google Scholar, 9Frit P. Bergmann E. Egly J.M. Biochimie (Paris). 1999; 81: 27-38Crossref PubMed Scopus (55) Google Scholar) that phosphorylates the cell cycle kinases on a threonine residue (Thr-161 of cdc2 or its equivalent) and activates them. A third subunit of CAK has been identified, termed MAT1. The MAT1 protein seems to act as an assembly factor, stimulating the activity of CAK by stabilizing the complex between the cdk7 and cycH subunits. MAT1 was subsequently found to be a component of TFIIH (3Hampsey M. Microbiol. Mol. Biol. Rev. 1998; 62: 465-503Crossref PubMed Google Scholar, 7Svejstrup J.Q. Vichi P. Egly J.M. Trends Biochem. Sci. 1996; 21: 346-350Abstract Full Text PDF PubMed Scopus (196) Google Scholar, 9Frit P. Bergmann E. Egly J.M. Biochimie (Paris). 1999; 81: 27-38Crossref PubMed Scopus (55) Google Scholar). MAT1 is the ortholog of yeast Tfb3 protein, suggesting that the triad of Tfb3-Kin28-Ccl1 may have similar functions in yeast and in animal cells. Mutations in TFB3 have been reported in a screen for mutants that are synthetic-lethal with a kin28-ts mutation (10Faye G. Simon M. Valay J.G. Fesquet D. Facca C. Mol. Gen. Genet. 1997; 255: 460-466Crossref PubMed Scopus (28) Google Scholar); the gene is named RIG2. Two mutants described in that report are severely and generally defective in transcription; each mutant bears multiple amino acid substitutions spread over the coding sequence. Another recent report shows that the tfb3-2 mutant is moderately sensitive to UV radiation, and is defective in nucleotide excision repair in vitro (11Feaver W.J. Huang W. Gileadi O. Myers L. Gustafsson C.M. Kornberg R.D. Friedberg E.C. J. Biol. Chem. 2000; 275: 5941-5946Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar). These data demonstrate that Tfb3p has multiple roles in transcription and DNA repair. The N terminus of TFB3 contains a cysteine-rich motif known as the RING or C3HC4 zinc motif (12Borden K.L. J. Mol. Biol. 2000; 295: 1103-1112Crossref PubMed Scopus (357) Google Scholar). The conserved RING motif folds into a compact domain in which two zinc ions are coordinated by the seven cysteines and one histidine (13Barlow P.N. Luisi B. Milner A. Elliott M. Everett R. J. Mol. Biol. 1994; 237: 201-211Crossref PubMed Scopus (253) Google Scholar, 14Gervais V. Busso D. Wasielewski E. Poterszman A. Egly J.M. Thierry J.C. Kieffer B. J. Biol. 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Full Text PDF PubMed Google and at the in and M. J.H. P. PubMed Scopus Google Scholar, P. PubMed Google Scholar) were the A the wild type TFB3 gene the TFB3 open reading frame is in was W. J. and into to and into to P. PubMed Google Scholar) was the and were J. was M. were and by a R. J. PubMed Scopus Google Scholar). A yeast with a was as gene was between the TFB3, and the was to the to gene by were with and for and The cells were and with a by a of the the is termed To mutants of TFB3, was in vitro with R. J. PubMed Scopus Google Scholar). of were to or in were on 5-fluoroorotic acid to for of the TFB3 gene on that to on at or at were identified, DNA was and the was was by the RING mutation into the TFB3 gene in gene C. S. A. in A Scholar). The TFB3 gene in was with C-terminal addition of of the by with a M. G. W. B. E. 1999; PubMed Scopus Google Scholar). The are termed respectively. The for were the and The for M. G. W. B. E. 1999; PubMed Scopus Google Scholar) contains of the by the on a reading cells at the for each were by and RNA was by with C. S. A. in A Scholar). The and of the RNA was by and by and of of each RNA was or to the For were to phase in at of each was to for of of with and and was as described at The were on yeast all yeast The were with and with the the of the were by the of the In the we of each which we the of of all on the of over were to be The data set is cells were in to the described in the to was as a to a of the in the To the cells were and in the of each was and the cells were in of and by addition of of For the cells were in and in For the cells were and with as described C. Sci. S. A. PubMed Scopus Google Scholar). and tfb3-2 were at to of each was and at for The cells were and cell were as described J.Q. W.J. J. Kornberg R.D. J. Biol. Chem. 1994; Full Text PDF PubMed Google Scholar). To the with TFIIH subunits, proteins were by of were in and with two were on and a of in were by a set of subunits of TFIIH. Two of the that subunits of TFIIH were and and were on a as were by and were by to a with of proteins in cells was a acid by of of protein G. M. Gileadi O. 2000; PubMed Scopus Google Scholar). A of at random and the of was into yeast cells. A was to the of the the of mutant to and mutants with a were one mutant or and two lethal mutants and Interestingly, of the mutant that all were of conserved cysteines of the RING which are involved in zinc and (12Borden K.L. J. Mol. Biol. 2000; 295: 1103-1112Crossref PubMed Scopus (357) Google P.N. Luisi B. Milner A. Elliott M. Everett R. J. Mol. Biol. 1994; 237: 201-211Crossref PubMed Scopus (253) Google Scholar). of the tfb3-2 that this mutant an to UV and is in nucleotide excision repair in vitro (11Feaver W.J. Huang W. Gileadi O. Myers L. Gustafsson C.M. Kornberg R.D. Friedberg E.C. J. Biol. 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However, the suggested to defect in cell cycle that may manifest at more than one in the cycle. To such we have an C. Sci. S. A. PubMed Scopus Google Scholar) to the of yeast in or mutant cells at were in phase by hydroxyurea an of DNA of the cells were to for to the mutant Tfb3 protein. the cells were to and was for an at and were to the the hydroxyurea A and or the at type cells to this of the to In the cells at the restrictive as cells that the cells were the cell cycle the in the mutant cells of the at DNA To the of the mutant we the of the and mutant Tfb3 To this we have the tfb3-2 mutation into the gene in we the TFB3 gene in the wild type and the mutant on with a the M. G. W. B. E. 1999; PubMed Scopus Google Scholar). Thus, Tfb3p and proteins could be an The the TFB3 type or gene were the by UV and cell cycle in the tfb3-2 mutant cell cycle similar to the at the restrictive acid protein phase and by The of Tfb3p is severely reduced in the mutant at the we the mutant at the restrictive temperature, a in the Tfb3 protein is as in other be is that the in the Tfb3p is a of the reduced of the mutant protein. The to TFIIH complex and processes, with of in the W.J. Gileadi O. Kornberg R.D. J. Biol. Chem. Full Text PDF PubMed Google Scholar, J.Q. W.J. J. Kornberg R.D. J. Biol. 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To into the of TFIIH we a that to the subunit and the of TFIIH by The on by be on a and of with The the the of the kinase subunit of TFIIH. Kin28p is with TFIIH and is in the in TFB3 wild type cells. In Kin28p is TFIIH in tfb3-2 mutant cells, and this is the cells are to a restrictive of the protein in tfb3-2 mutant cells is for the with TFIIH. These which were in and with on the not that the of Kin28p with TFIIH in tfb3-2 mutant cells is not an of the of Tfb3p in the kinase to the TFIIH or in stabilizing the The of Tfb3p in that Tfb3p with the TFIIH and not with is in with by W.J. J.Q. Kornberg R.D. 1994; Full Text PDF PubMed Scopus Google Scholar). A recent study by and V. S. Mol. Biol. PubMed Scopus Google Scholar) reported the of a yeast complex similar to mammalian have not such a we its the of on the of the tfb3-2 mutation on the of Kin28p are in with on with in cells, Tfb3p the of of Kin28p by A. Gileadi O. Mol. Biol. 1998; PubMed Scopus Google Scholar). These that the of Kin28p may be required for assembly or for of the between TFIIH and the kinase subunits. Busso D. A. B. Poterszman A. Gileadi O. Egly J.M. J. Biol. Chem. 2000; 275: Full Text Full Text PDF PubMed Scopus Google Scholar) reported the of in MAT1 protein on the of TFIIH in cells. In MAT1 the substitutions to the as well as of the RING domain in vitro transcription. The between the of the mutation in MAT1 of and Tfb3 transcriptional may be to the of the and yeast proteins or to the the of the of Busso D. A. B. Poterszman A. Gileadi O. Egly J.M. J. Biol. Chem. 2000; 275: Full Text Full Text PDF PubMed Scopus Google Scholar) that the in TFIIH in the yeast mutant are not to the in the of to on the of the mutant protein. mutants of of the general transcription factors are severely defective in (3Hampsey M. Microbiol. Mol. Biol. 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For example, cells in to the to the restrictive at DNA At of of cells is for to wild type cells UV or for in not These are to the data to that the mutant cells in The mutant cells are sensitive to and moderately sensitive to UV Interestingly, the tfb3-2 mutant bears to the of the mutant P. A. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar); the cells are are at more than one in the cells cycle are generally to and the is the Another mutant another set of with large at the restrictive Valay J.G. G. C. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). to the of the we a reduced of not we this of the cells at restrictive temperature, which may be to an Another between and TFIIH is that is a mutant is with of the mutants A. Gileadi O. Mol. Biol. 1998; PubMed Scopus Google Scholar). is required for the of Kin28p A. Gileadi O. Mol. Biol. 1998; PubMed Scopus Google the two proteins are at cellular P. M. E. J. 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Jona et al. (Tue,) studied this question.