TFIIS is required for the balanced expression of the genes encoding ribosomal components under transcriptional stress. Researchers utilized Cellena
Fernando Gómez-Herreros, Lola de Miguel-Jiménez, Macarena Morillo-Huesca, Lidia Delgado-Ramos, María C. Muñoz-Centeno and Sebastián Chávez*
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avda Reina Mercedes 6. E-41012 Seville, Spain
Received February 18, 2011; Revised April 4, 2012; Accepted April 5, 2012
ABSTRACT
Transcription factor IIS (TFIIS) stimulates RNA cleavage by RNA polymerase II by allowing backtracked enzymes to resume transcription elongation.
Yeast cells do not require TFIIS for viability, unless ,they suffer severe transcriptional stress due to NTP-depleting drugs
like 6-azauracil ormycophenolic acid. In order to broaden our knowledge on the role of TFIIS under transcriptional stress, we carried out a genetic screening for suppressors of TFIIS-lacking cells’ sensitivity to 6-azauracil and mycophenolic acid. Five suppressors were identified, four of which were related to the transcriptional regulation of those genes encoding ribosomal components [rRNAs and ribosomal proteins (RP)], including global regulator SFP1. This led us to discover that RNA polymerase II
is hypersensitive to the absence of TFIIS under NTP iscarcity conditions when transcribing RP genes. The absence of Sfp1 led to a profound alteration of the transcriptional response to NTP-depletion, thus allowing the expression of RP genes to resist these
stressful conditions in the absence of TFIIS. We discuss the effect of transcriptional stress on ribosome biogenesis and propose that TFIIS contributes to prevent a transcriptional imbalance between rDNA and RP gene.
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