The Drosophila extramacrochaetae protein antagonizes sequence-specific DNA binding by daughterless/achaete-scute protein complexes.
In Drosophila, a group of regulatory proteins of the helix-loop-helix (HLH) class play an essential role in conferring upon cells in the developing adult epidermis the competence to give rise to sensory organs. Proteins encoded by the daughterless (da) gene and three genes of the achaete-scute complex (AS-C) act positively in the determination of the sensory organ precursor cell fate, while the extramacrochaetae (emc) and hairy (h) gene products act as negative regulators. In the region upstream of the achaete gene of the AS-C, we have identified three 'E box' consensus sequences that are bound specifically in vitro by hetero-oligomeric complexes consisting of the da protein and an AS-C protein. We have used this DNA-binding activity to investigate the biochemical basis of the negative regulatory function of emc. Under the conditions of our experiments, the emc protein, but not the h protein, is able to antagonize specifically the in vitro DNA-binding activity of da/AS-C and putative da/da protein complexes. We interpret these results as follows: the heterodimerization capacity of the emc protein (conferred by its HLH domain) allows it to act in vivo as a competitive inhibitor of the formation of functional DNA-binding protein complexes by the da and AS-C proteins, thereby reducing the effective level of their transcriptional regulatory activity within the cell.
Van Doren
M
M
Department of Biology, University of California San Diego, La Jolla 92093-0322.
Ellis
H M
HM
Posakony
J W
JW
D000818:Animals; D001345:Autoradiography; D051792:Basic Helix-Loop-Helix Proteins; D001665:Binding Sites / Q000502:physiology; D015342:DNA Probes; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism* / Q000494:pharmacology*; D004330:Drosophila / Q000196:embryology; D029721:Drosophila Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D005821:Genetic Techniques; D007301:Insect Hormones / Q000378:metabolism* / Q000494:pharmacology; D019476:Insect Proteins; D009024:Morphogenesis / Q000187:drug effects; D009687:Nuclear Proteins / Q000494:pharmacology; D010525:Peripheral Nerves / Q000196:embryology; D014176:Protein Biosynthesis / Q000502:physiology; D012097:Repressor Proteins; D012679:Sense Organs / Q000196:embryology; D014157:Transcription Factors / Q000494:pharmacology
D051792:Basic Helix-Loop-Helix Proteins; D015342:DNA Probes; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D007301:Insect Hormones; D019476:Insect Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C090080:Da protein, Drosophila; C063577:emc protein, Drosophila; C489235:hairy protein, Drosophila; C061841:hairy protein, insect