Gene activation and DNA binding by Drosophila Ubx and abd-A proteins.
The Ubx and abd-A gene products are required for proper development of thoracic and abdominal structures in Drosophila. We expressed LexA-Ubx and LexA-abdA fusion proteins in yeast. These proteins activated expression of target genes that carried either upstream LexA operators or upstream Ubx binding sites. Both proteins contain homeodomains. Experiments with mutant fusion proteins show that the homeodomain is not required for the proteins to form dimers or enter the nucleus, and that, when DNA binding is provided by the LexA moiety, the homeodomain is not required for gene activation. Our results suggest that the homeodomain is necessary for these proteins to bind Ubx sites, but that the homeodomain does not contact DNA exactly like bacterial helix-turn-helix proteins. Finally, our data suggest that gene activation by these proteins is a simple consequence of their binding to DNA, while negative gene regulation requires that these proteins act together with other Drosophila gene products.
Samson
M L
ML
Department of Molecular Biology, Massachusetts General Hospital, Boston 02114.
Jackson-Grusby
L
L
Brent
R
R
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics*; D005786:Gene Expression Regulation; D005801:Genes, Homeobox; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae / Q000235:genetics; D012697:Serine Endopeptidases; D014157:Transcription Factors / Q000235:genetics*; D015533:Transcriptional Activation; D000099160:LexA Repressor Protein
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D012697:Serine Endopeptidases; D014157:Transcription Factors; D000099160:LexA Repressor Protein