Regulation of transcriptional repression by Nrg1 and Nrg2.
Cristin D. Berkey (1), Valmik K. Vyas (2), Marian Carlson (3)
(1) Genetics and Development, Columbia University, 701 West 168 Street , New York, NY 10032, USA;
(2) Integrated Program in Cellular, Molecular and Biophysical Studies, Columbia University, 701 West 168 Street, New York, NY 10032, USA;
(3) Genetics and Development, Columbia University, 701 West 168 Street, New York, NY, 10032, USA
The Nrg1 and Nrg2 repressors of S. cerevisiae have very similar zinc fingers and closely related functions in glucose repression. We show that NRG1 and NRG2 are differently regulated in response to carbon source at the RNA and protein levels. Expression of NRG1 RNA and protein is glucose-repressed. NRG2 RNA levels are relatively constant during glucose limitation or growth in nonfermentable carbon sources, but Nrg2 protein levels are diminished. Chromatin immunoprecipitation assays showed that Nrg1 and Nrg2 bind DNA in the absence of glucose, suggesting that glucose signals regulate their repressor functions rather than their binding to DNA. Microarray data showed that loss of either repressor leads to derepression of many target genes to levels comparable to those observed in the double nrg1 nrg2 mutant. In a repression assay, overexpressed Nrg2 represses more strongly in the presence of overexpressed Nrg1. These findings suggest that the regulation of repression is complex. We are investigating the possibility that interaction between these two repressors plays a role in conferring repression.
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