Analysis of the role of SLIK complex in Pol II rRNA synthesis in Saccharomyces cerevisiae
Although rRNA is synthesized by Pol I under normal physiological conditions, stress conditions trigger the synthesis of rRNA by Pol II in Saccharomyces cerevisiae. Mitochondrial dysfunction triggers the polymerase switch; however, basal levels of Pol II rRNA synthesis are present in ρ + cells growing in non-limiting carbon and nitrogen conditions. Both the Retrograde pathway and the Hog pathway are required for basal Pol II rRNA synthesis (Sagar, 2008). Although Rtg1p and Rtg3p are activated by Rtg2p, neither play a role in Pol II rRNA synthesis; instead Rtg2p and other members of the SLIK histone acetylase complex are crucial for Pol II rRNA synthesis. During elongation SLIK is retained in the elongation complex perhaps replacing the elongator complex to allow more efficient elongation of Pol II transcribed rRNA. Thus, chromatin structure plays a crucial role in the selection between Pol I and Pol II for rRNA synthesis.