The role of Rvb proteins in transcription of galactose induced genes in yeast
The Rvb proteins (Rvb1 and Rvb2) are essential, evolutionarily conserved nuclear proteins that have homologues in all Eukaryotes. They are ATPases of the AAA+ family and together form a double circular hexamer. The ATPase activity of Rvb is essential for the cell but not necessary for all of Rvb´s functions. Rvb has various roles in cells including DNA repair, chromatin remodelling, maturation of telomerase complexes and regulation of transcription.
To better understand the function of Rvb we have chosen to focus on its role in transcription. We show that Rvb is necessary for the expression of galactose induced genes (GAL genes). Rvb2 does not have an effect on the binding of the transcription factor Gal4 to GAL1/10 UAS (upstream activator sequence). Furthermore we show that Rvb2 is necessary for recruitment of RNA polymerase II to the actively transcribed GAL genes. Degradation of Rvb2 leads to reduced binding of the Mediator complex, TFIIH, and TBP to the GAL10 promoter. Interestingly the ATPase activity of Rvb2 is not necessary for its role in GAL gene expression.
The mediator is necessary for recruitment of TFIIH, TBP, RNA pol II and the full induction of GAL and we conclude that Rvb2 participates in the recruitment of this complex thereby facilitating the transcription of galactose induced genes.