Regulation of Skn7-dependent, oxidative stress-induced genes by the RNA polymerase II-CTD phosphatase, Fcp1, and Mediator kinase subunit, Cdk8, in yeast.

Fcp1 is a protein phosphatase that facilitates transcription elongation and termination by dephosphorylating the C-terminal domain of RNA polymerase II. High-throughput genetic screening and gene expression profiling of mutants revealed a novel connection to Cdk8, the Mediator complex kinase subunit, and Skn7, a key transcription factor in the oxidative stress response pathway. Briefly, Skn7 was enriched as a regulator of genes whose mRNA levels were altered in and Δ mutants and was required for the suppression of mutant growth defects by loss of under oxidative stress conditions. Targeted analysis revealed that mutating decreased Skn7 mRNA and protein levels as well as its association with target gene promoters but paradoxically increased the mRNA levels of Skn7-dependent oxidative stress-induced genes ( and ) under basal and induced conditions. The latter was in part recapitulated via chemical inhibition of transcription in WT cells, suggesting that a combination of transcriptional and posttranscriptional effects underscored the increased mRNA levels of and observed in the mutant. Interestingly, loss of robustly normalized the mRNA levels of Skn7-dependent genes in the mutant background and also increased Skn7 protein levels by preventing its turnover. As such, our work suggested that loss of could overcome transcriptional and/or posttranscriptional alterations in the mutant through its regulatory effect on Skn7. Furthermore, our work also implicated and in the broader response to environmental stressors in yeast.