Abstract
When exploited as cell factories, Saccharomyces cerevisiae cells are exposed to harsh environmental stresses impairing titer, yield and productivity of the fermentative processes. The development of robust strains therefore represents a pivotal challenge for the implementation of cost-effective bioprocesses. Altering master regulators of general cellular rewiring represents a possible strategy to evoke shaded potential that may accomplish the desirable features. The poly(A) binding protein Pab1, as stress granules component, was here selected as the target for obtaining widespread alterations in mRNA metabolism, resulting in stress tolerant phenotypes. Firstly, we demonstrated that the modulation of Pab1 levels improves robustness against different stressors. Secondly, the mutagenesis of PAB1 and the application of a specific screening protocol on acetic acid enriched medium allowed the isolation of the further ameliorated mutant pab1 A60-9. These findings pave the way for a novel approach to unlock industrially promising phenotypes through the modulation of a post-transcriptional regulatory element.
Highlights
To proteins in different messenger ribonucleoprotein complexes, which regulate their translation, turnover and subcellular localization[20]
Further researches will help to elucidate the reasons of the ameliorated phenotype, we speculate that it could be at least partially related to the altered stress granules (SG) morphology, and especially with the longer persistence of these structures, which offer a storage compartmentalization for mRNA
V322L is localized at the beginning of the RRM4 domain, which has been described to interact with proteins implied in mRNA export from the nucleus, and R492S is in correspondence of the P domain, which is critical for Pab[1] self-association and mediates poly(A) tail deadenylation performed by the Ccr4-NOT complex[44,45]
Summary
To proteins in different messenger ribonucleoprotein (mRNP) complexes, which regulate their translation, turnover and subcellular localization[20]. Translating mRNAs are usually trapped into polysomes, while non-translating mRNAs can accumulate in mRNA-protein complexes named processing bodies (P-bodies) and stress granules (SG)[18,21,22]. We demonstrated that the overexpression of PAB1 on a centromeric plasmid increases S. cerevisiae resistance to different stresses commonly occurring during industrial fermentations. This robust phenotype was further improved through the selection of a mutant version of Pab[1], under selective pressure for acetic acid tolerance. An effect on SG morphology was observed
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