Transcriptional regulation of carbon utilization in yeast

酿酒酵母优先使用葡萄糖作为碳源。当葡萄糖耗尽时，这种酵母可以使用非糖类碳水化合物(非发酵性碳水化合物)，如乙醇、乳酸和醋酸酯。这导致了基因表达的大规模重新编程，以适应新的碳源。这个过程是由主激酶Snf1控制的，它可以磷酸化包括转录因子Cat8和Sip4在内的各种底物，这些转录因子通过与靶基因启动子中的碳源反应元件结合来控制特定基因的表达。例如，这些因素上调了PCK1的表达，PCK1编码一种非常重要的糖异生酶。Cat8和Sip4属于锌簇蛋白Gal4家族，在酵母中形成了一类重要的转录调控因子。我们通过对锌簇蛋白RDS2进行全基因组定位(CHIP-CHIP)来鉴定该蛋白，发现它是糖异生的重要调节因子。然而，RDS2和Cat8显示的共同靶基因数量有限。因此，它们具有特定和共同的功能。我们还鉴定了另一个锌簇基因，我们将其命名为ERT1(乙醇翻译调节因子)。芯片分析表明，在乙醇条件下，该因子与一些糖异生基因(如PCK1)、核糖体蛋白基因以及编码线粒体成分的基因以及编码参与RNA聚合酶III转录的TFIIIC复合体两个亚基的基因相结合。也有证据表明，另一种锌簇蛋白Gsm1也参与控制基因表达，以适应非发酵碳源。显然，葡萄糖耗竭后基因表达的调节是一个比最初预期的更复杂的过程。这一建议旨在更好地描述转录因子RDS2、ERT1、Cat8、Sip4和Gsm1的作用。更具体地说，我们将：1)确定ERT1在葡萄糖或乙醇作为碳源时的作用2)研究Gsm1的功能3)确定RDS2、ERT1、Cat8、Sip4和Gsm1在调节乙醇、乳酸、甘油和乙酸盐作为碳源的利用中的相对贡献和相互作用。

The yeast Saccharomyces cerevisiae preferentially uses glucose as a carbon source. Upon glucose exhaustion, this yeast can use non-sugar carbons (non-fermentable carbons) such as ethanol, lactate and acetate. This results in massive reprogramming of gene expression to adapt to the new carbon source. This process is controlled by the master kinase Snf1 which phosphorylates various substrates including the transcription factors Cat8 and Sip4 that control expression of specific genes by binding to Carbon Source Response Elements found in the promoters of the target genes. For example, these factors upregulate the expression of PCK1 encoding a very important enzyme for gluconeogenesis. Cat8 and Sip4 belong to the Gal4 family of zinc cluster proteins that form an important class of transcriptional regulators in yeast. We have characterized the zinc cluster protein Rds2 by performing genome-wide localization (ChIP-chip) of this factor and found that it is a very important regulator of gluconeogenesis. However, Rds2 and Cat8 show a limited number of common target genes. Thus, they have specific and common functions. We are also characterizing another zinc cluster gene we named ERT1 (for Ethanol Regulator of Translation). ChIP-chip analysis shows that under ethanol conditions, this factor binds to some gluconeogenic genes (e.g. PCK1), ribosomal proteins genes as well as genes encoding mitochondrial components and two genes encoding two subunits of the TFIIIC complex involved in RNA polymerase III transcription. There is also evidence that another zinc cluster protein, Gsm1, is also involved in controlling gene expression for adaptation to a non-fermentable carbon source. Clearly, regulation of gene expression following glucose exhaustion is a more complex process than initially anticipated. This proposal is aimed at better characterizing the role of the transcription factors Rds2, Ert1, Cat8, Sip4, and Gsm1. More specifically we will: 1) Determine the role of Ert1 with glucose or ethanol as carbon sources 2) Study the function of Gsm1 3) Determine the relative contribution and the interplay of Rds2, Ert1, Cat8, Sip4 and Gsm1 in mediating utilization of ethanol, lactate, glycerol, and acetate as carbon sources.