ADR1 is a yeast transcription factor that contains two zinc fingers of the Cys-2-His-2 (C2H2) class. Mutations that change the specificity of DNA binding of ADR1 to its target site, upstream activation sequence 1 (UAS1), have been identified at three positions in the first zinc finger. Mutations Arg-115 to Gln, His-118 to Thr, and Arg-121 to Asn led to new specificities of DNA binding at adjacent positions 10, 9, and 8 (3'-GAG-5') in UAS1. Arg-115 is at the finger tip, and His-118 and Arg-121 are at positions 3 and 6, respectively, in the alpha helix of finger 1. One double mutant displayed the binding specificity expected from the properties of its constituent new-specificity mutations. Mutations in the second finger that allowed its binding site to be identified through loss-of-contact phenotypes were made. These mutations imply a tail-to-tail orientation of the two ADR1 monomers on their adjacent binding sites. Finger 1 is aligned on UAS1 in an amino-to-carboxyl-terminal orientation along the guanine-rich strand in a 3'-to-5' direction. One of the ADR1 mutants was functional in vivo with both its cognate binding site and wild-type UAS1, but the other two mutants were defective in transactivation despite their ability to bind with high affinity to their cognate binding sites.

• PMID: 1588970
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Journal Article | Research Support, U.S. Gov't, P.H.S.

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Thukral SK, Morrison ML, Young ET

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