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Transcription Regulation in Layers

During eukaryotic transcription activation, transcription factors, activators, and coactivators bind to and remodel DNA, resulting in the recruitment of TATA-binding protein and RNA polymerase II. Previous studies in yeast have shown that the DNA binding transcriptional activators Adr1 and Cat8 bind to the alcohol dehydrogenase II (ADH2) promoter and activate ADH2 transcription when cells are placed in low glucose, in a process that requires the AMP-dependent kinase Snf1. In this study, Christine Tachibana and colleagues exploit the previous observation that, under glucose repression conditions, Adr1 and Cat8 bind constitutively (in a Snf1-dependent manner) to the ADH2 promoter in yeast lacking the histone deacetylase (HDAC) genes, HDA1 and RPD3.

Snf1 acts at a step after RNA Pol II binding.

The authors obtain evidence that Adr1 and Cat8 recruit RNA polymerase II and its requisite transcriptional machinery to the ADH2 promoter under glucose repression conditions in yeast lacking HDACs, but that transcription does not occur. They make the interesting observation that glucose repression of ADH2 can be completely relieved in yeast lacking HDACs by deletion of the PP1 phosphatase subunit Reg1, which negatively regulates Snf1 kinase activity, and by replacement of Adr1 with a S230A mutant that cannot be phosphorylated. Based on their data, the authors argue that derepression of ADH2 transcription involves activation of a poised RNA polymerase II initiation complex by Snf1, thus demonstrating that biological regulation is achieved not at any one step but through the superimposition of several layers of regulation.

FOOTNOTES

See referenced article, J. Biol. Chem. 2007, 282, 37308-37315

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