林 紗千子

Saccharomyces cerevisiae is widely used as a model organism for eukaryotic cells and generally prefers fermentation rather than respiration even under an aerobic environment. Only when glucose is exhausted, S. cerevisiae switches to aerobic respiration via massive reprogramming of gene expression accompanying that. These gene-expression changes are not simply achieved by the transcriptional level, rather multiple post-transcriptional regulatory steps are also involved. This chapter outlines how budding yeast cells coordinate energy metabolisms based on gene expression, with a focus on the intricate interplay of multiple post-transcriptional regulatory mechanisms. Especially, it includes the roles of RNA-binding proteins as well as non-coding RNAs for post-transcriptional regulations.

Saccharomyces cerevisiae has six synonymous tRNATrpCCA genes encoding the identical sequence, including their intronic region. They are supposed to express tRNATrpCCA in the same quality and quantity. Here, we generated single to quintuple deletion strains with all the possible combinations of the synonymous tRNATrpCCA genes to analyze whether those individual genes equally contribute cell viability and tRNA production. The quintuple deletion strains that only harbor tW(CCA)J, tW(CCA)M, or tW(CCA)P were viable but almost lethal while the other quintuple deletions showed moderately impaired growth. Theses growth differences were not obvious among the quadruple deletion strains, which expressed almost one third of mature tRNATrpCCA in the wild type. Therefore, no dosage compensation operates for tRNATrpCCA amount, and growth variations among the quintuple deletion strains may not simply reflect differences in tRNATrpCCA shortage. Yeast may retain the redundancy of tRNATrpCCA genes for a noncanonical function(s) beyond supply of the tRNA to translation.