TFIIH is indispensable for nucleotide excision repair (NER) and RNA polymerase II transcription. Its tenth subunit was recently discovered in yeast as Tfb5. Unlike other TFIIH subunits, Tfb5 is not essential for cell survival. We have analyzed the role of Tfb5 in NER. NER was deficient in the tfb5 deletion mutant cell extracts, and was specifically complemented by purified Tfb5 protein. In contrast to the extreme ultraviolet (UV) sensitivity of rad14 mutant cells that lack any NER activity, tfb5 deletion mutant cells were moderately sensitive to UV radiation, resembling that of the tfb1-101 mutant cells in which TFIIH activity is compromised but not eliminated. Thus, Tfb5 protein directly participates in NER and is an accessory NER protein that stimulates the repair to the proficient level. Lacking a DNA binding activity, Tfb5 was found to interact with the core TFIIH subunit Tfb2, but not with other NER proteins. The Tfb5 - Tfb2 interaction was correlated with the cellular NER function of Tfb5, supporting the functional importance of this interaction. Our results led to a model in which Tfb5 acts as an architectural stabilizer conferring structural rigidity to the core TFIIH such that the complex is maintained in its functional architecture.
|Number of pages||11|
|Journal||Nucleic Acids Research|
|State||Published - Feb 2007|
Bibliographical noteFunding Information:
The authors thank Jeffrey A. Ranish for the yeast tfb5 deletion mutant and its isogenic wild-type strains, Stephen Buratowski for the tfb1-101 mutant and its isogenic wild-type strains and Errol C. Friedberg for the yeast Y190 strain and plasmid vectors pAS2 and pACT2. This work was supported by the NIH grant CA67978. Funding to pay the Open Access publication charges for this article was provided by the NIH grant CA67978.
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