Division of Molecular and Cellular Biology, Department of Supramolecular Biology, Graduate School of Nanobioscience, Yokohama City University, 1-7-29, Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
Genes Cells. 2010 Dec;15(12):1169-88. doi: 10.1111/j.1365-2443.2010.01452.x. Epub 2010 Oct 26.
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-N568Δ, 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-N568Δ strains and facilitates the continuous transcription of CLN2 after heat shock in the taf1-N568Δ 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.
在酿酒酵母中，TFIID 由 TATA 结合蛋白（TBP）和一组 TBP 相关因子（TAFs）组成，介导大多数 II 类基因的转录。先前的研究表明，CLN2 的表达在 taf1-ts2 中显著降低，但在 taf1-N568Δ 中没有降低，尽管这两种突变在其他基因中显示出相似的温度敏感生长表型和转录缺陷。在这里，我们表明 CLN2 的表达减少不是由于先前实验中 taf1 等位基因的差异，而是由于宿主菌株中 SSD1 基因座的等位基因差异。具体来说，当与 taf1 结合时，ssd1-d 会降低 CLN2 的表达。来自 SSD1-V 的 Ssd1p，而不是来自 ssd1-d 的 Ssd1p，在野生型和 taf1-N568Δ 菌株中稳定 CLN2 mRNA 的亚群，并在 taf1-N568Δ 菌株中热激后促进 CLN2 的连续转录。报告基因实验表明，这两种活性似乎都依赖于 CLN2 mRNA 的 5'-非翻译区，并且 Ssd1p 通过其氨基末端和羧基末端结构域与该区域结合。基于这些观察结果，我们提出了 Ssd1p 作用的模型，并讨论了其生物学作用。
