The Saccharomyces cerevisiae GATA Factors Dal80p and Deh1p Can Form Homo- and Heterodimeric Complexes

GATA family proteins Gln3p, Gat1p, Dal80p, and Deh1p mediate the regulation of nitrogen catabolite repression (NCR)-sensitive gene expression in Saccharomyces cerevisiae. Thus far, Gln3p, Dal80p, and Deh1p have been shown to bind to GATA sequences in NCR-sensitive promoters, in some cases to exactly the same GATA sequences. A minimal Gln3p binding site consists of a single GATA sequence, whereas a Dal80p binding site consists of two GATA sequences in specific orientation, 15 to 35 bp apart, suggesting that Dal80p may bind to DNA as a dimer. Additionally, both Dal80p and Deh1p are predicted to contain a leucine zipper motif near their C termini. Therefore, we tested whether they could form homo- and/or heterodimers in two-hybrid assays. We show that Dal80p-Dal80p, Dal80p-Dal80pLZ (leucine zipper), Dal80pLZ-Dal80pLZ, Dal80p-Deh1pLZ, Dal80pLZ-Deh1pLZ, and Deh1pLZ-Deh1pLZ complexes can form. Dal80p-Dal80p and Dal80pLZ-Dal80pLZ complexes yield 5- to 10-fold stronger signals than the other possible dimers. If Dal80p and Deh1p bind to DNA only after dimerization, then the difference in ability to form complexes could significantly affect their affinity for binding DNA and thus the degree of regulation exerted by each of the two factors.