ADA3, a putative transcriptional adaptor, consists of two separable domains and interacts with ADA2 and GCN5 in a trimeric complex.

Mutations in yeast ADA2, ADA3, and GCN5 weaken the activation potential of a subset of acidic activation domains. In this report, we show that their gene products form a heterotrimeric complex in vitro, with ADA2 as the linchpin holding ADA3 and GCN5 together. Further, activation by LexA-ADA3 fusions in vivo ...
are regulated by the levels of ADA2. Combined with a prior observation that LexA-ADA2 fusions are regulated by the levels of ADA3 (N. Silverman, J. Agapite, and L. Guarente, Proc. Natl. Acad. Sci. USA 91:11665-11668, 1994), this finding suggests that these proteins also form a complex in cells. ADA3 can be separated into two nonoverlapping domains, an amino-terminal domain and a carboxyl-terminal domain, which do not separately complement the slow-growth phenotype or transcriptional defect of a delta ada3 strain but together supply full complementation. The carboxyl-terminal domain of ADA3 alone suffices for heterotrimeric complex formation in vitro and activation of LexA-ADA2 in vivo. We present a model depicting the ADA complex as a coactivator in which the ADA3 amino-terminal domain mediates an interaction between activation domains and the ADA complex.
Mesh Terms:
Blotting, Western, Cloning, Molecular, DNA-Binding Proteins, Fungal Proteins, Gene Expression Regulation, Fungal, Genes, Fungal, Histone Acetyltransferases, Macromolecular Substances, Mutagenesis, Protein Biosynthesis, Protein Kinases, Recombinant Proteins, Saccharomyces cerevisiae Proteins, Transcription Factors, Transcription, Genetic
Mol. Cell. Biol.
Date: Mar. 01, 1995
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