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Mol. Cell. Biol., 01 1995, 208-216, Vol 15, No. 1
L Kuras and D Thomas
Transcription of the genes necessary for sulfur amino acid biosynthesis in
Saccharomyces cerevisiae is dependent on Met4, a transcriptional activator
that belongs to the basic region-leucine zipper protein family. In this
report, we show that one mechanism permitting the repression of the sulfur
network by S-adenosylmethionine (AdoMet) involves inhibition of the
transcriptional activation function of Met4. Using a wide array of deleted
LexA-Met4 fusion proteins as well as various Gal4-Met4 hybrids, we identify
the functional domains of Met4 and characterize their relationship. Met4
appears to contain only one activation domain, located in its N-terminal
part. We demonstrate that this activation domain functions in a
constitutive manner and that AdoMet responsiveness requires a distinct
region of Met4. Furthermore, we show that when fused to a heterologous
activation domain, this inhibitory region confers inhibition by AdoMet.
Met4 contains another distinct functional domain that appears to function
as an antagonist of the inhibitory region when intracellular AdoMet is low.
On the basis of the presented results, a model for intramolecular
regulation of Met4 is proposed.
Copyright © 1995, American Society for Microbiology
Functional analysis of Met4, a yeast transcriptional activator responsive to S-adenosylmethionine
Centre de Genetique Moleculaire, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
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