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Molecular and Cellular Biology, April 2007, p. 2821-2829, Vol. 27, No. 8
0270-7306/07/$08.00+0 doi:10.1128/MCB.02159-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
Received 17 November 2006/ Returned for modification 19 December 2006/ Accepted 31 January 2007
Transcriptional regulation of IMD2 in yeast (Saccharomyces cerevisiae) is governed by the concentration of intracellular guanine nucleotide pools. The mechanism by which pool size is measured and transduced to the transcriptional apparatus is unknown. Here we show that DNA sequences surrounding the IMD2 initiation site constitute a repressive element (RE) involved in guanine regulation that contains a novel transcription-blocking activity. When this regulatory region is placed downstream of a heterologous promoter, short poly(A)+ transcripts are generated. The element is orientation dependent, and sequences within the normally transcribed and nontranscribed regions of the element are required for its activity. The promoter-proximal short RNAs are unstable and serve as substrates for the nuclear exosome. These findings support a model in which intergenic short transcripts emanating from upstream of the IMD2 promoter are terminated by a polyadenylation/terminator-like signal embedded within the IMD2 transcription start site.
Published ahead of print on 12 February 2007.
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