Saccharomyces cerevisiae Ssd1p promotes CLN2 expression by binding to the 5′‐untranslated region of CLN2 mRNA

Abstract

In Saccharomyces cerevisiae, TFIID, which is composed of TATA-binding protein (TBP) and a set of TBP-associated factors (TAFs), mediates the transcription of most class II genes. Previous studies have shown that CLN2 expression was significantly reduced by taf1-ts2, but not by taf1-N568D, although both mutations display similar temperature-sensitive growth phenotypes and transcriptional defects in other genes. Here, we show that the reduced expression of CLN2 is not because of differences in taf1 alleles in the previous experiments but because of allelic differences at the SSD1 locus in the host strains. Specifically, ssd1-d reduces CLN2 expression when combined with taf1. Ssd1p expressed from SSD1-V, but not from ssd1-d, stabilizes a subpopulation of CLN2 mRNA in wild-type and taf1-N568D strains and facilitates the continuous transcription of CLN2 after heat shock in the taf1-N568D strain. Reporter assays show that both activities appear to depend on the 5¢-untranslated region of CLN2 mRNA and that Ssd1p binds to this region via its amino-and carboxy-terminal domains. Based on these observations, we propose a model for the action of Ssd1p and discuss its biologic role.

Trans-Kingdom Horizontal DNA Transfer from Bacteria to Yeast Is Highly Plastic Due to Natural Polymorphisms in Auxiliary Nonessential Recipient Genes

“…The pRS313 vector, which was used for complementation analysis, was provided by the National Bio-Resource Project (NBRP) of MEXT, Japan. The SSD1-V and ssd1-d constructs were provided by Dr. T. Kokubo [17]. The helper plasmid pDPT51 was provided by Dr. Y. Fujita (Graduate School of Bioagricultural Science, Nagoya University, Nagoya, Japan).…”

The Relationship between Chromosomal Positioning within the Nucleus and theSSD1Gene inSaccharomyces cerevisiae

“…Ssd1p binds transcripts of the genes related to cell-wall organization and the CLN2 gene, and regulates the expression of these genes. [33][34][35] The signals of bud morphogenesis and cell-cycle progression regulated by Ssd1p are believed to be associated closely with the precise chromosomal positioning, or unknown transcripts associated with Ssd1p play a role in the precise chromosomal positioning. The other possibility is that Ssd1p within the nucleus regulates chromosomal positioning by interacting with the factor responsible for the precise positioning, or by regulating the transcription of the genes related to chromosomal positioning by associating with RNA polymerase II.…”

Cell Morphogenesis Proteins Are Translationally Controlled through UTRs by the Ndr/LATS Target Ssd1

“…A number of Ssd1-associated transcripts are asymmetrically localized in proliferating cells [20]–[21], and Ssd1 has been implicated in subcellular localization of one of these ( SRL1 ) [9]. At least one Ssd1-associated message, CLN2 , is stabilized by Ssd1 binding to its 5′ untranslated region [22]. It is not known if Cbk1 regulates Ssd1-mediated stabilization of CLN2 or if this 5′UTR-mediated association is related to Ssd1's function as a translational repressor.…”

“…It is unclear how Ssd1 associates with mRNAs, and understanding this could illuminate what dictates the composition of Ssd1-containing mRNPs. The motif A[G/U]UCAUUCCUU is significantly enriched in 5′ untranslated regions of mRNAs that associate with Ssd1 in affinity purification experiments [5], and a portion of the CLN2 5′UTR containing a sequence matching this motif mediates Ssd1 association [22]. For brevity, we refer to this motif as the “SEE” ( S sd1 E nriched E lement).…”