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Mol. Cell. Biol., Jul 1995, 3934-3944, Vol 15, No. 7
SR Hepworth, LK Ebisuzaki and J Segall
Sporulation of the yeast Saccharomyces cerevisiae represents a simple
developmental process in which the events of meiosis and spore wall
formation are accompanied by the sequential activation of temporally
distinct classes of genes. In this study, we have examined expression of
the SPS4 gene, which belongs to a group of genes that is activated midway
through sporulation. We mapped the upstream boundary of the regulatory
region of SPS4 by monitoring the effect of sequential deletions of
5'-flanking sequence on expression of plasmid-borne versions of SPS4
introduced into a MATa/MAT alpha delta sps4/delta sps4 strain. This
analysis indicated that the 5' boundary of the regulatory region was within
50 bp of the putative TATA box of the gene. By testing various
oligonucleotides that spanned this boundary and the downstream sequence for
their ability to activate expression of a heterologous promoter, we found
that a 15-bp sequence sufficed to act as a sporulation-specific upstream
activation sequence. This 15-bp fragment, designated UASSPS4, activated
expression of a CYC1-lacZ reporter gene midway through sporulation and was
equally active in both orientations. Extending the UAS fragment to include
the adjacent 14-bp enhanced its activity 10-fold. We show that expression
of SPS4 is regulated in a manner distinct from that of early meiotic genes:
mutation of UME6 did not lead to vegetative expression of SPS4, and
sporulation-specific expression was delayed by mutation of IME2. In vivo
and in vitro assays suggested that a factor present in vegetative cells
bind to the UASSPS4 element. We speculate that during sporulation this
factor is modified to serve as an activator of the SPS4 gene or,
alternatively, that it recruits an activator to the promoter.
Copyright © 1995, American Society for Microbiology
A 15-base-pair element activates the SPS4 gene midway through sporulation in Saccharomyces cerevisiae
Department of Biochemistry, University of Toronto, Ontario, Canada.
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