ADA3, a putative transcriptional adaptor, consists of two separable domains and interacts with ADA2 and GCN5 in a trimeric complex
Department of Medicine, Division of Infectious Diseases and Immunology
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
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.
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Citation: Mol Cell Biol. 1995 Mar;15(3):1203-9. Link to article on publisher's site