title: Uncoupling dorsal-mediated activation from dorsal-mediated repression in the Drosophila embryo.
abstract: The Rel family transcription factor Dorsal patterns the dorsoventral axis of the Drosophila embryo by activating genes such as twist and snail and repressing genes such as decapentaplegic and zerknüllt. Dorsal represses transcription by recruiting the co-repressor Groucho. However, repression occurs only when Dorsal-binding sites are close to binding sites for other factors that also bind Groucho. The need for additional factors to assist Dorsal in repression may result from the intrinsically weak interaction between Dorsal and Groucho. To test this idea, we generated a Dorsal variant containing a high-affinity Groucho recruitment motif at its C terminus. As predicted, this variant functions as a dedicated repressor, silencing decapentaplegic and zerknüllt while failing to activate twist and snail. We also converted Dorsal into a dedicated activator by replacing its weak Groucho-recruitment motif with heterologous activation domains. Although the dedicated activator alleles fail to repress decapentaplegic and zerknüllt in the syncytial blastoderm embryo, they are able to pattern the dorsoventral axis. This indicates that dorsoventral patterning is not dependent upon Dorsal-mediated repression, reflecting the existence of redundant mechanisms to block Decapentaplegic signaling.
authors.affiliation: Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, CA 90095-1569, USA.
authors.forename: Girish S
authors.initials: GS
authors.lastname: Ratnaparkhi
authors.forename: Songtao
authors.initials: S
authors.lastname: Jia
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Courey
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000378:metabolism; D019521:Body Patterning / Q000235:genetics* / Q000502:physiology; D004330:Drosophila / Q000196:embryology*; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D018507:Gene Expression Regulation, Developmental / Q000235:genetics* / Q000502:physiology; D018398:Homeodomain Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D014162:Transfection; D051879:Twist-Related Protein 1 / Q000378:metabolism
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012097:Repressor Proteins; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D051879:Twist-Related Protein 1; C497753:Twi protein, Drosophila; C085607:Zen protein, Drosophila; C062236:dl protein, Drosophila; C064196:dpp protein, Drosophila; C091023:gro protein, Drosophila; C000604451:sna protein, Drosophila