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Mol Cell Biol, April 1998, p. 1985-1995, Vol. 18, No. 4
Faculty of Biology,
Received 23 September 1997/Returned for modification 13 November
1997/Accepted 30 December 1997
IME1 encodes a transcriptional activator required for
the transcription of meiosis-specific genes and initiation of meiosis in Saccharomyces cerevisiae. The transcription of
IME1 is repressed in the presence of glucose, and a low
basal level of IME1 RNA is observed in vegetative cultures
with acetate as the sole carbon source. Upon nitrogen depletion a
transient induction in the transcription of IME1 is
observed in MATa/MAT
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Multiple and Distinct Activation and Repression
Sequences Mediate the Regulated Transcription of IME1, a
Transcriptional Activator of Meiosis-Specific Genes in
Saccharomyces cerevisiae


diploids but not in
MAT-insufficient strains. In this study we demonstrate that the
transcription of IME1 is controlled by an extremely unusual
large 5' region, over 2,100 bp long. This area is divided into four
different upstream controlling sequences (UCS). UCS2 promotes the
transcription of IME1 in the presence of a nonfermentable
carbon source. UCS2 is flanked by three negative regions: UCS1, which
exhibits URS activity in the presence of nitrogen, and UCS3 and UCS4,
which repress the activity of UCS2 in MAT-insufficient cells. UCS2
consists of alternate positive and negative elements: three distinct
constitutive URS elements that prevent the function of any upstream
activating sequence (UAS) under all growth conditions, a constitutive
UAS element that promotes expression under all growth conditions, a UAS
element that is active only in vegetative media, and two discrete
elements that function as UASs in the presence of acetate. Sequence
analysis of IME1 revealed the presence of two almost identical 30- to 32-bp repeats. Surprisingly, one repeat, IREd, exhibits constitutive URS activity, whereas the other repeat, IREu,
serves as a carbon-source-regulated UAS element. The RAS-cyclic AMP-dependent protein kinase cAPK pathway prevents the UAS activity of
IREu in the presence of glucose as the sole carbon source, while the
transcriptional activators Msn2p and Msn4p promote the UAS activity of
this repeat in the presence of acetate. We suggest that the use of
multiple negative and positive elements is essential to restrict
transcription to the appropriate conditions and that the combinatorial
effect of the entire region leads to the regulated transcription of
IME1.
*
Corresponding author. Mailing address: Faculty of
Biology, Technion, Haifa, 32000 Israel. Phone: 972-4-8294214. Fax:
972-4-8225153. E-mail:
ykassir{at}techunix.technion.ac.il.
Present address: Whitehead Institute, Cambridge, MA.
Present address: Department of Molecular Biology, Massachusetts
General Hospital, Boston, MA.
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