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Mol. Cell. Biol., Nov 1995, 6109-6117, Vol 15, No. 11
J Deckert, AM Rodriguez Torres, JT Simon and RS Zitomer
Rox1 is a repressor of the hypoxic genes of Saccharomyces cerevisiae. It
binds to a specific hypoxic consensus sequence in the upstream region of
these genes and represses transcription in conjunction with the general
repression complex Tup1-Ssn6. In this study, we demonstrated that the first
100 amino acids comprising the HMG domain of Rox1 were responsible for DNA
binding and that when bound, Rox1 bent DNA at an angle of 90 degrees. A
mutational analysis resulted in the isolation of seven missense mutations,
all located within the HMG domain, that caused loss of DNA binding. The
effect of these mutations on the structure of Rox1 was evaluated on the
basis of the homology between Rox1 and the human male sex-determining
protein SRY, for which a structural model is available. The failure to
isolate missense mutations in the carboxy-terminal three-quarters of the
protein prompted a deletion analysis of this region. The results suggested
that this region was responsible for the repression function of Rox1 and
that the repression information was redundant. This hypothesis was
confirmed by using a set of fusions between sequences encoding the GAL4
DNA-binding domain and portions of ROX1. Those fusions containing either
the entire carboxy-terminal region or either half of it were capable of
repression. Repression by selected fusions was demonstrated to be dependent
on Ssn6.
Copyright © 1995, American Society for Microbiology
Mutational analysis of Rox1, a DNA-bending repressor of hypoxic genes in Saccharomyces cerevisiae
Department of Biological Sciences, University of Albany/State University of New York 12222, USA.
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