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Molecular and Cellular Biology, January 1999, p. 882-888, Vol. 19, No. 1
School of Biological Sciences, The University
of Manchester, Manchester M13 9PT, United Kingdom
Received 25 August 1998/Returned for modification 1 October
1998/Accepted 19 October 1998
Saccharomyces cerevisiae responds to pyrimidine
starvation by increasing the expression of four URA genes,
encoding the enzymes of de novo pyrimidine biosynthesis, three- to
eightfold. The increase in gene expression is dependent on a
transcriptional activator protein, Ppr1p. Here, we investigate the
mechanism by which the transcriptional activity of Ppr1p responds to
the level of pyrimidine biosynthetic intermediates. We find that
purified Ppr1p is unable to promote activation of transcription in an
in vitro system. Transcriptional activation by Ppr1p can be observed,
however, if either dihydroorotic acid (DHO) or orotic acid (OA) is
included in the transcription reactions. The transcriptional activation function and the DHO/OA-responsive element of Ppr1p localize to the
carboxyl-terminal 134 amino acids of the protein. Thus, Ppr1p directly
senses the level of early pyrimidine biosynthetic intermediates within
the cell and activates the expression of genes encoding proteins
required later in the pathway. These results are discussed in terms of
(i) regulation of the pyrimidine biosynthetic pathway and (ii) a novel
mechanism of regulating gene expression.
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Activation of Transcription by Metabolic
Intermediates of the Pyrimidine Biosynthetic Pathway
*
Corresponding author. Mailing address: School of
Biological Sciences, The University of Manchester, 2.205 Stopford
Building, Oxford Road, Manchester M13 9PT, United Kingdom. Phone:
44-161-275-5317. Fax: 44-161-275-5082. E-mail:
Richard.Reece{at}man.ac.uk.
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