Mediator subunits and histone methyltransferase Set2 contribute to Ino2-dependent transcriptional activation of phospholipid biosynthesis in the yeast Saccharomyces cerevisiae
- 353 Downloads
To activate eukaryotic genes, several pathways which modify chromatin and recruit general factors of the transcriptional machinery are utilized. We investigated the factors required for activation of yeast phospholipid biosynthetic genes, depending on activator protein Ino2 which binds to the inositol/choline-responsive element (ICRE) upstream promoter motif together with its partner protein Ino4. We used a set of 15 strains each defective for one of the non essential subunits of yeast mediator complex and identified med2, med3, med15, med18 and med19 as impaired for inositol biosynthesis. In these mutants, ICRE-dependent gene activation was reduced to 13–22% of the wild-type level. We also demonstrate synthetic growth and activation defects among mediator mutants and mutants lacking defined histone modifications (snf1, gcn5) and transcriptional coactivators (sub1). Analysis of mutants defective for histone methylation (set1, set2 and dot1) and demethylation (jhd1, jhd2, gis1, rph1 and ecm5) revealed the importance of the H3 Lys36-specific Set2 methyltransferase for ICRE-dependent gene expression. Although defined mediator subunits are critical for gene activation, we could not detect their interaction with Ino2. In contrast, Ino2 directly binds to the Set2 histone methyltransferase. Mapping of interaction domains revealed the importance of the SET core domain which was necessary and sufficient for binding Ino2.
KeywordsPhospholipid biosynthesis Saccharomyces cerevisiae Transcriptional activation Ino2 Mediator Histone methyltransferase
This work has been supported by the Deutsche Forschungsgemeinschaft (DFG). We thank Christian Schultz for support.
- Dietz M, Heyken WT, Hoppen J, Geburtig S, Schüller HJ (2003) TFIIB and subunits of the SAGA complex are involved in transcriptional activation of phospholipid biosynthetic genes by the regulatory protein Ino2 in the yeast Saccharomyces cerevisiae. Mol Microbiol 48:1119–1130PubMedCrossRefGoogle Scholar
- Drysdale CM, Jackson BM, McVeigh R, Klebanow ER, Bai Y, Kokubo T, Swanson M, Nakatani Y, Weil PA, Hinnebusch AG (1998) The Gcn4p activation domain interacts specifically in vitro with RNA polymerase II holoenzyme, TFIID, and the Adap-Gcn5p coactivator complex. Mol Cell Biol 18:1711–1724PubMedGoogle Scholar
- Schüller HJ, Schorr R, Hoffmann B, Schweizer E (1992) Regulatory gene INO4 of yeast phospholipid biosynthesis is positively autoregulated and functions as a trans-activator of fatty acid synthase genes FAS1 and FAS2 from Saccharomyces cerevisiae. Nucleic Acids Res 20:5955–5961PubMedCrossRefGoogle Scholar
- Schwank S, Ebbert R, Rautenstrauss K, Schweizer E, Schüller HJ (1995) Yeast transcriptional activator INO2 interacts as an Ino2p/Ino4p basic helix-loop-helix heteromeric complex with the inositol/choline-responsive element necessary for expression of phospholipid biosynthetic genes in Saccharomyces cerevisiae. Nucleic Acids Res 23:230–237PubMedCrossRefGoogle Scholar