Berkey Cristin D, Vyas Valmik K, Carlson Marian
Department of Genetics and Development, Columbia University, New York, New York 10032, USA.
Eukaryot Cell. 2004 Apr;3(2):311-7. doi: 10.1128/EC.3.2.311-317.2004.
The Nrg1 and Nrg2 repressors of Saccharomyces cerevisiae have highly similar zinc fingers and closely related functions in the regulation of glucose-repressed genes. We show that NRG1 and NRG2 are differently regulated in response to carbon source at both the RNA and protein levels. Expression of NRG1 RNA is glucose repressed, whereas NRG2 RNA levels are nearly constant. Nrg1 protein levels are elevated in response to glucose limitation or growth in nonfermentable carbon sources, whereas Nrg2 levels are diminished. Chromatin immunoprecipitation assays showed that Nrg1 and Nrg2 bind DNA both in the presence and absence of glucose. In mutant cells lacking the corepressor Ssn6(Cyc8)-Tup1, promoter-bound Nrg1, but not Nrg2, functions as an activator in a reporter assay, providing evidence that the two Nrg proteins have distinct properties. We suggest that the differences in expression and function of these two repressors, in combination with their similar DNA-binding domains, contribute to the complex regulation of the large set of glucose-repressed genes.
酿酒酵母的Nrg1和Nrg2阻遏物具有高度相似的锌指结构，并且在葡萄糖阻遏基因的调控中具有密切相关的功能。我们发现，NRG1和NRG2在RNA和蛋白质水平上对碳源的响应具有不同的调控方式。NRG1 RNA的表达受葡萄糖阻遏，而NRG2 RNA水平几乎恒定。Nrg1蛋白水平在葡萄糖限制或在不可发酵碳源中生长时升高，而Nrg2水平则降低。染色质免疫沉淀分析表明，无论有无葡萄糖，Nrg1和Nrg2均能结合DNA。在缺乏共阻遏物Ssn6（Cyc8）-Tup1的突变细胞中，在报告基因检测中，启动子结合的Nrg1而非Nrg2起激活剂的作用，这证明这两种Nrg蛋白具有不同的特性。我们认为，这两种阻遏物在表达和功能上的差异，连同它们相似的DNA结合结构域，有助于对大量葡萄糖阻遏基因进行复杂的调控。
