Abstract
Loc1 and Puf6, which are localized predominantly to the nucleus, are required for the localization and translational repression of the ASH1 mRNA in the yeast, Saccharomyces cerevisiae. During its transport to the daughter cell, the ASH1 mRNA is translationally repressed via associations with She2, Loc1, and Puf6. Here, we investigated the roles of Loc1 and Puf6 in the translation of mRNAs other than that encoding ASH1. In loc1 or puf6 deletion strains, expression of the mating-specific transcription factor, Ste12, was significantly increased at the post-transcriptional level. These phenotypes required the 5’ untranslated region (UTR) of STE12, which carries the putative Puf6-binding sequences. The RNA helicase, Dhh1, which is a known positive regulator for the translation of STE12 mRNA, was found to be functionally connected with Loc1 and Puf6 in the context of Ste12 expression. Our results collectively show that the phosphorylation of the N-terminal Thr16 residue of Dhh1 affects the protein interactions of Dhh1 with Loc1 or Puf6, and consequently regulates Ste12 expression.
Highlights
MRNAs are transcribed in the nucleus and transported to the cytoplasm, where they direct protein synthesis
These results suggest that Loc1 and Puf6 repressed the expression of STE12 at the posttranscriptional level
We show that Puf6 and Loc1 mediate the translational repression of the STE12 mRNA, and that these roles are functionally connected with Dhh1, which acts as a positive regulator for STE12 mRNA translation
Summary
MRNAs are transcribed in the nucleus and transported to the cytoplasm, where they direct protein synthesis. Saccharomyces cerevisiae, the Ash protein has been reported to be asymmetrically localized in daughter cells to repress the transcription of HO endonuclease, which is crucial for the mating type switch [1,2,3]. The ASH1 mRNA is transcribed in the mother cell and transported to the distal tip of the daughter cell, where the protein is translated. During this transport, the translation of the ASH1 mRNA is repressed by its associations with RNA-binding proteins such as She, Puf, Loc, and Khd1 [4,5,6,7,8].
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