Genetic interactions between TFIIF and TFIIS

¹ University of California, Berkeley
² SUNY, Buffalo
³ University of Texas, M.D. Anderson
⁴ University of British Columbia

^* To whom correspondence should be addressed. E-mail: kanecm{at}berkeley.edu.

Submitted on April 1, 2006
Revised on April 24, 2006
Accepted on 28 April 2006

	Abstract

The eukaryotic transcript elongation factor TFIIS is encoded by a non-essential gene, PPR2, in Saccharomyces cerevisiae. Disruptions of PPR2 are lethal in conjunction with a disruption in the non-essential gene TAF14/TFG3. While investigating which of the Taf14p-containing complexes may be responsible for the synthetic lethality between ppr2 and taf14 , we discovered genetic interactions between PPR2 and both TFG1 and TFG2, encoding the two larger subunits of the TFIIF complex that also contains Taf14p. Mutant alleles of tfg1 or tfg2 that render cells cold-sensitive have improved growth at low temperature in the absence of TFIIS. Remarkably, the amino-terminal 130 amino acids of TFIIS, which are dispensable for the known in vitro and in vivo activities of TFIIS, are required to complement the lethality in taf14 ppr2 cells. Analyses of deletion and chimeric gene constructs of PPR2 implicate contributions by different regions of this N-terminal domain. No strong common phenotypes were identified for the ppr2 and taf14 strains, implying that the proteins are not functionally redundant. Instead, the absence of Taf14p in the cell appears to create a dependence on an undefined function of TFIIS mediated by its N-terminal region. This region of TFIIS is also at least in part responsible for the deleterious effect of TFIIS on tfg1 or tfg2 cold-sensitive cells. Together, these results suggest a physiologically relevant functional connection between TFIIS and TFIIF.

Key Words: TFIIF, TFIIS, synthetic interactions, transcript elongation, yeast

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