Fine-Tuning of Histone H3 Lys4 Methylation During Pseudohyphal Differentiation by the CDK Submodule of RNA Polymerase II

Abstract

Transcriptional regulation is dependent upon the interactions between the RNA pol II holoenzyme complex and chromatin. RNA pol II is part of a highly conserved multiprotein complex that includes the core mediator and CDK8 subcomplex. In Saccharomyces cerevisiae, the CDK8 subcomplex, composed of Ssn2p, Ssn3p, Ssn8p, and Srb8p, is thought to play important roles in mediating transcriptional control of stress-responsive genes. Also central to transcriptional control are histone post-translational modifications. Lysine methylation, dynamically balanced by lysine methyltransferases and demethylases, has been intensively studied, uncovering significant functions in transcriptional control. A key question remains in understanding how these enzymes are targeted during stress response. To determine the relationship between lysine methylation, the CDK8 complex, and transcriptional control, we performed phenotype analyses of yeast lacking known lysine methyltransferases or demethylases in isolation or in tandem with SSN8 deletions. We show that the RNA pol II CDK8 submodule components SSN8/SSN3 and the histone demethylase JHD2 are required to inhibit pseudohyphal growth-a differentiation pathway induced during nutrient limitation-under rich conditions. Yeast lacking both SSN8 and JHD2 constitutively express FLO11, a major regulator of pseudohyphal growth. Interestingly, deleting known FLO11 activators including FLO8, MSS11, MFG1, TEC1, SNF1, KSS1, and GCN4 results in a range of phenotypic suppression. Using chromatin immunoprecipitation, we found that SSN8 inhibits H3 Lys4 trimethylation independently of JHD2 at the FLO11 locus, suggesting that H3 Lys4 hypermethylation is locking FLO11 into a transcriptionally active state. These studies implicate the CDK8 subcomplex in finetuning H3 Lys4 methylation levels during pseudohyphal differentiation.?

Characterization of the Candida albicans Amino Acid Permease Family: Gap2 Is the Only General Amino Acid Permease and Gap4 Is an S -Adenosylmethionine (SAM) Transporter Required for SAM-Induced Morphogenesis

“…SAM is known to function as a methyl donor, and therefore it may affect methylation of DNA, histones, or other proteins that may result in the yeast-to-hypha transition. Whereas for C. albicans there are few data, for S. cerevisiae results have been obtained that clearly link histone methylation with pseudohyphal growth (52). Previously, we showed that methionine is a strong inducer of morphogenesis (38).…”

Gene transcription as a limiting factor in protein production and cell growth

“…Cells deleted of the Mediator Kinase inhibitory sub-complex are pseudo-hyphal and flocculate when growing in liquid media (Hengartner et al, 1995; Holstege et al, 1998). This phenotype is reverted by deleting components of the Mediator tail or head sub-complexes (Gonzalez et al, 2014; Jeronimo et al, 2016; Law et al, 2015; Palecek et al, 2000; van de Peppel et al, 2005)(Figure 4A, Figure S4A). We therefore asked whether protein burden similarly reverts the flocculation phenotype of kinase-deleted cells.…”

Choose Your Own Adventure: The Role of Histone Modifications in Yeast Cell Fate

“…The HAT Gcn5 has been reported to negatively regulate ICR1 expression, thereby promoting FLO11 transcriptional activation [85], most likely through regulation of a second ncRNA. Additionally, deletion of the demethylase JHD2 or a component of the CDK8 submodule of RNA pol II, SSN8 , results in elevated H3K4me3 near the FLO11 transcription start site (TSS) and constitutive activation of FLO11 [86]. These data suggest a direct role for H3K4me3 in FLO11 activation, although its potential contribution to lncRNA-dependent regulation of FLO11 has not yet been investigated.…”