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 or mycophenolic 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 scarcity 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 
genes.