A complex containing RNA polymerase II, Paf1p, Cdc73p, Hpr1p, and Ccr4p plays a role in protein kinase C signaling

Yeast contains at least two complex forms of RNA polymerase II (Pol II) one including the Srbps and a second biochemically distinct form defined by th e presence of Paf1p and Cdc73p (X. Shi et al,, Mel. Cell. Biol. 17:1160-116 9, 1997). In this work we demonstrate that Ccr4p and Hpr1p are components o f the Paf1p-Cdc73p-Pol II complex. We have found many synthetic genetic int eractions between factors within the Paf1p-Cdc73p complex, including the le thality of paf1 Delta ccr4 Delta, paf1 Delta hpr1 Delta, ccr4 Delta hpr1 De lta, and ccr4 Delta gal11 Delta double mutants, In addition, paf1 Delta and ccr4 Delta are lethal in combination with srb5 Delta, indicating that the factors within and between the two RNA polymerase II complexes have overlap ping essential functions. We have used differential display to identify sev eral genes whose expression is affected by mutations in components of the P af1p-Cdc73p-Pol II complex. Additionally, as previously observed for hrp1 D elta, deleting PAF1 or CDC73 leads to elevated recombination between direct repeats. The paf1 Delta and ccr4 Delta mutations, as well as gal11 Delta, demonstrate sensitivity to cell wall-damaging agents, rescue of the tempera ture-sensitive phenotype by sorbitol, and reduced expression of genes invol ved in cell wall biosynthesis. This unusual combination of effects on recom bination and cell wall integrity has also been observed for mutations in ge nes in the Pkc1p-Mpk1p kinase cascade. Consistent with a role for this nove l form of RNA polymerase II in the Pkc1p-Mpk1p signaling pathway, we find t hat paf1 Delta mpk1 Delta and paf1 Delta pkc1 Delta double mutants do not d emonstrate an enhanced phenotype relative to the single mutants. Our observ ation that the Mpk1p kinase is fully active in a paf1 Delta strain indicate s that the Paf1p-Cdc73p complex may function downstream of the Pkc1p-Mpk1p cascade to regulate the expression of a subset of yeast genes.