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Mol. Cell. Biol., 03 1995, 1220-1233, Vol 15, No. 3
CM Drysdale, E Duenas, BM Jackson, U Reusser, GH Braus and AG Hinnebusch
GCN4 is a transcriptional activator in the bZIP family that regulates amino
acid biosynthetic genes in the yeast Saccharomyces cerevisiae. Previous
work suggested that the principal activation domain of GCN4 is a highly
acidic segment of approximately 40 amino acids located in the center of the
protein. We conducted a mutational analysis of GCN4 with a single-copy
allele expressed under the control of the native promoter and translational
control elements. Our results indicate that GCN4 contains two activation
domains of similar potency that can function independently to promote
high-level transcription of the target genes HIS3 and HIS4. One of these
domains is coincident with the acidic activation domain defined previously;
the other extends over the N- terminal one-third of the protein. Both
domains are partially dependent on the coactivator protein ADA2. Each
domain appears to be composed of two or more small subdomains that have
additive effects on transcription and that can cooperate in different
combinations to promote high-level expression of HIS3 and HIS4. At least
three of these subdomains are critically dependent on bulky hydrophobic
amino acids for their function. Five of the important hydrophobic residues,
Phe-97, Phe-98, Met-107, Tyr-110, and Leu-113, fall within a region of
proposed sequence homology between GCN4 and the herpesvirus acidic
activator VP16. The remaining three residues, Trp-120, Leu-123, and
Phe-124, are highly conserved between GCN4 and its Neurospora counterpart,
cpc- 1.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
The transcriptional activator GCN4 contains multiple activation domains that are critically dependent on hydrophobic amino acids
Section on Molecular Genetics of Lower Eukaryotes, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
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