Tfb5 interacts with Tfb2 and facilitates nucleotide excision repair in yeast

Abstract

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.

In vivo interactions of TTDA mutant proteins within TFIIH

“…Previously, it was shown in vitro that an N-terminally truncated TTDA protein without the first 14 amino acids (TTDADN14) is unable to interact with p52 (Zhou et al, 2007). Indeed, we do not observe interaction between TTDA M1T (lacking the first 15 amino acids of TTDA) and p52 (Fig.…”

Control of the function of the transcription and repair factor TFIIH by the action of the cochaperone Ydj1

“…A good example is given by a 3D view in Fig. 5B in which the residues previously published as essential for Tfb2-Tfb5 interaction (36,37) are highlighted. Such residues fall within Ydj1-binding consensus motives, facing each other in a mirrorlike distribution to allow contact between molecules (Fig.…”

“…5A, arrowheads). Reciprocally, the seven residues that compose the motif in Tfb5/TTDA are essential to interact with Tfb2/p52 (37,36) (Fig. 5A, arrowheads).…”

Cross Talk between Cellular Regulatory Networks Mediated by Shared Proteins

“…TTDA is the tenth TFIIH subunit and it specifically functions in DNA repair. The interaction of TTDA with the TFIIH core components p52 and XPB stimulates the ATPase activity of XPB, anchoring TFIIH to the damaged DNA [20,[35][36][37][38] reviewed in [16]. Once bound, the interaction between the other TFIIH components p34, p44, and XPD stimulates the XPD helicase activity [39,40].…”