Ubiquitin ligase Rsp5p is involved in the gene expression changes during nutrient limitation in Saccharomyces cerevisiae

摘要

Rsp5p is an essential ubiquitin ligase involved in many different cellular events, including amino acid transporters degradation, transcription initiation and mRNA export. It plays important role in both stress resistance and adaptation to the change of nutrients. We have found that ubiquitination machinery is necessary for the correct induction of the stress response SPI1 gene at the entry of the stationary phase. SPI1 is a gene whose expression is regulated by the nutritional status of the cell and whose deletion causes hypersensitivity to various stresses, such as heat shock, alkaline stress and oxidative stress. Its regulation is mastered by Rsp5p, as mutations in this gene lead to a lower SPI1 expression. In this process, Rsp5p is helped by several proteins, such as Rsp5p-interacting proteins Bul1p/2p, the ubiquitin conjugating protein Ubc1p and ubiquitin proteases Ubp4p and Ubp16p. Moreover, a mutation in the RSP5 gene has a global effect at the gene expression level when cells enter the stationary phase. Rsp5p particularly controls the levels of the ribosomal proteins mRNAs at this stage. Rsp5p is also necessary for a correct induction of p-bodies under stress conditions, indicating that this protein plays an important role in the post-transcriptional fate of mRNA under nutrient starvation.