Project description:The switch from cellular proliferation to differentiation occurs to a large extend through specific programs of gene expression. In fission yeast, the high-mobility-group transcription factor Ste11 is the master regulator of sexual differentiation. ste11 is induced by environmental conditions, mostly nitrogen starvation, leading to mating and meiosis 1. We have used ChIP-chip and gene expression profiling to show that CDK-dependent phosphorylation of serine 2 in the C-terminal domain (CTD) of the largest subunit of the RNA polymerase II (PolII) holoenzyme plays a critical role in the induction of ste11 transcription during sexual differentiation while it has a minor impact on gene expression during vegetative growth. Moreover, we demonstrate that both the recruitment of the CTD serine 2 kinase and the phosphorylation event initiate at the promoter region of ste11 in contrast to the classical case where serine 2 phosphorylation occurs across the coding region 2. In the absence of CTD serine 2 phosphorylation, both PolII occupancy at the ste11 locus, and ste11 expression are impaired. This results in sterility that is rescued when ste11 is expressed from the canonical adh promoter. We conclude that a modification of the RNA polymerase II holoenzyme plays a specific and pivotal role in the sexual differentiation. For the ChIP-chip experiments, 3-4 biological replicates were performed for each tagged protein of interest. For the expression experiments, two biological samples were hybridized for each mutant strain (replicates 1 and 2), with two dye-swap technical replicates per sample (replicates 3 and 4).
Project description:Dynamic post-translational modification of RNA polymerase II (RNAPII) coordinates the co-transcriptional recruitment of enzymatic complexes that regulate chromatin states and co-transcriptional processing of nascent RNA. Extensive phosphorylation of serine residues occurs at the structurally-disordered C-terminal domain (CTD) of the largest RNAPII subunit, which is composed of multiple heptapeptide repeats with consensus sequence Y1-S2-P3-T4-S5-P6-S7. Serine-5 and Serine-7 phosphorylation mark transcription initiation, whereas Serine-2 phosphorylation coincides with productive elongation. In vertebrates, the CTD has eight non-canonical substitutions of Serine-7 into Lysine-7, which can be acetylated (K7ac). Here, we describe for the first time mono- and di-methylation of CTD Lysine-7 residues (K7me1 and K7me2). K7me1 and K7me2 are observed during the earliest transcription stages and precede or accompany Serine-5 and Serine-7 phosphorylation. Genome wide mapping of 2 novel RNAPII post-translational modifications (CTD-K7me1 and CTD-K7me2) in mouse ES cells.
