Protein Arginine Methylation Facilitates Environmental Adaptation in the Budding Yeast Saccharomyces cerevisiae
Bijoo Davis, Richoo
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Cells need to adapt to a constantly changing environment in order to survive and thrive. They are able to do so by continually modulating their gene expression profile to meet challenges posed by these environmental stressors. While there are multiple stages at which cells can regulate their gene expression, regulation at the level of transcription is the most common mode. Despite much work devoted to understanding the fundamental switches and mechanisms underlying transcriptional regulation, many of the nuances in transcriptional regulation are not well understood, and scientists have only begun to appreciate the intricate details that formulate the molecular basis for fine-tuning transcriptional output. My work described here reveals a novel role for the budding yeast protein arginine methyltransferase enzyme, Hmt1, in fine-tuning the transcription of tRNA genes in response to stress. Hmt1 methylates the RNA Pol III specific subunit Rpc31, wherein the methyl marks promote interaction between Pol III and its repressor Maf1 and thereby facilitates the repression of Pol III transcription in response to stress. We have also identified a role for Hmt1 in the adaptation of yeast cells to fermentable carbon sources. As a survival strategy, yeast cells prefer the use of fermentation over respiration when presented with abundance of glucose and oxygen. Hmt1 promotes this strategy by suppressing respiration. Additionally, in the presence of abundant glucose when yeast cells carry out fermentation, Hmt1 suppresses the expression of many genes associated with mitochondrial functioning that promote respiration. This reduction in expression could decrease the abundance of proteins required for respiratory growth and accordingly increase the glycolytic flux through the fermentation pathway that provides a competitive advantage for the budding yeast in its natural habitat.