Direct homeodomain-DNA interaction in the autoregulation of the fushi tarazu gene.
A major problem in the elucidation of the molecular mechanisms governing development is the distinction between direct and indirect regulatory interactions among developmental control genes. In vivo studies have indicated that the Drosophila segmentation gene fushi tarazu (ftz) directly or indirectly autoregulates its expression. Here we describe a generally applicable experimental approach which establishes a direct in vivo interaction of the homeodomain protein ftz with the ftz cis-autoregulatory control region. In vitro studies have shown that the DNA-binding specificity of the ftz homeodomain can be changed by a single amino-acid substitution in the recognition helix (Gln 50----Lys). Whereas wild-type ftz homeodomain binds preferentially to a CCATTA motif, the mutant homeodomain (ftzQ50K) recognizes a GGATTA motif. We now find that the in vivo activity of an ftz autoregulatory enhancer element is reduced by mutations of putative ftz-binding sites to GGATTA. This down-regulatory effect is specifically suppressed in vivo by the DNA-binding specificity mutant ftzQ50K. These results establish a direct positive autoregulatory feedback mechanism in the regulation of this homeobox gene.
Schier
A F
AF
Biozentrum der Universität Basel, Switzerland.
Gehring
W J
WJ
D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D004247:DNA / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D004330:Drosophila / Q000235:genetics* / Q000254:growth & development*; D029721:Drosophila Proteins; D004742:Enhancer Elements, Genetic; D005246:Feedback; D051717:Fushi Tarazu Transcription Factors; D005786:Gene Expression Regulation / Q000502:physiology*; D005796:Genes / Q000502:physiology*; D018398:Homeodomain Proteins; D007301:Insect Hormones / Q000096:biosynthesis* / Q000235:genetics*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid
D029721:Drosophila Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; D007301:Insect Hormones; C497169:ftz protein, Drosophila; D004247:DNA