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Mol. Cell. Biol., Apr 1996, 1557-1566, Vol 16, No. 4
ZW Sun and M Hampsey
An ssu72 mutant of Saccharomyces cerevisiae was identified as an enhancer
of a TFIIB defect (sua7-1) that confers both a cold-sensitive growth defect
and a downstream shift in transcription start site selection. The ssu72-1
allele did not affect cold sensitivity but, in combination with sua7-1,
created a heat-sensitive phenotype. Moreover, start site selection at the
ADH1 gene was dramatically shifted further downstream of the normal sites.
Both of these effects could be rescued by either SUA7 or SSU72, thereby
defining a functional relationship between the two genes. SSU72 is a
single-copy, essential gene encoding a novel protein of 206 amino acids.
The ssu72-1 allele is the result of a 30-bp duplication creating a sequence
encoding a Cys-X2-Cys-X6-Cys-X2- Cys zinc binding motif near the N terminus
of Ssu72p. Mutational analysis demonstrated that the N terminus of Ssu72p
is essential for function and that cysteine residues in both the normal and
mutant proteins are critical. We discuss the possibility that the potential
zinc binding motif of Ssu72 facilitates assembly of the transcription
preinitiation complex and that this effect is important for accurate start
site selection in vivo.
Copyright © 1996, American Society for Microbiology
Synthetic enhancement of a TFIIB defect by a mutation in SSU72, an essential yeast gene encoding a novel protein that affects transcription start site selection in vivo
Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, Shreveport, 71130, USA.
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