Abstract
The S. cerevisiae Pop2 protein is an exonuclease in the Ccr4-Not complex that is a conserved regulator of gene expression. Pop2 regulates gene expression post-transcriptionally by shortening the poly(A) tail of mRNA. A previous study has shown that Pop2 is phosphorylated at threonine 97 (T97) by Yak1 protein kinase in response to glucose limitation. However, the physiological importance of Pop2 phosphorylation remains unknown. In this study, we found that Pop2 is phosphorylated at serine 39 (S39) under unstressed conditions. The dephosphorylation of S39 was occurred rapidly after glucose depletion, and the addition of glucose to the glucose-deprived culture recovered this phosphorylation, suggesting that Pop2 phosphorylation at S39 is regulated by glucose. This glucose-regulated phosphorylation of Pop2 at S39 is dependent on Pho85 kinase. We previously reported that Pop2 takes a part in the cell wall integrity pathway by regulating LRG1 mRNA; however, S39 phosphorylation of Pop2 is not involved in LRG1 expression. On the other hand, Pop2 phosphorylation at S39 is involved in the expression of HSP12 and HSP26, which encode a small heat shock protein. In the medium supplemented with glucose, Pop2 might be phosphorylated at S39 by Pho85 kinase, and this phosphorylation contributes to repress the expression of HSP12 and HSP26. Glucose starvation inactivated Pho85, which resulted in the derepression of HSP12 and HSP26, together with other glucose sensing mechanisms. Our results suggest that Pho85-dependent phosphorylation of Pop2 is a part of the glucose sensing system in yeast.
Highlights
IntroductionPost-transcriptional regulation, including the control of mRNA degradation and translation, plays important roles in regulation of gene expression
To confirm that the band shifts are caused by Pop2 phosphorylation, immunoprecipitated Pop2Flag were treated with λ-phosphatases
Since the phosphorylation of Pop2 at serine 39 (S39) is regulated by glucose availability as described above (Fig 2), we examined whether expression of HSP12 and HSP26 are affected by glucose availability
Summary
Post-transcriptional regulation, including the control of mRNA degradation and translation, plays important roles in regulation of gene expression. Pop is reportedly involved in expression control of glucose-repressed genes and regulation of the cell wall integrity (CWI) pathway in S. cerevisiae [3, 4]. The loss of POP2 results in pleiotropic phenotypes including temperature-sensitive growth, abnormal cell morphology, weak cell lysis and defective glucose repression [3, 5]. Pop is phosphorylated by Yak kinase at threonine 97 (T97) in response to a glucose-regulating signal [6]. This modification is required for cell growth control and cell cycle arrest at G1 phase after glucose starvation [6]. The LRG1 mRNA level is elevated in pop2Δ and the high temperature-sensitivity phenotype caused by pop2Δ mutation is suppressed by deletion of LRG1 [4]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
