The Torso signaling pathway modulates a dual transcriptional switch to regulate tailless expression.
The Torso (Tor) signaling pathway activates tailless (tll) expression by relieving tll repression. None of the repressors identified so far, such as Capicuo, Groucho and Tramtrack69 (Ttk69), bind to the tor response element (tor-RE) or fully elucidate tll repression. In this study, an expanded tll expression pattern was shown in embryos with reduced heat shock factor (hsf) and Trithorax-like (Trl) activities. The GAGA factor, GAF encoded by Trl, bound weakly to the tor-RE, and this binding was enhanced by both Hsf and Ttk69. A similar extent of expansion of tll expression was observed in embryos with simultaneous knockdown of hsf, Trl and ttk69 activities, and in embryos with constitutively active Tor. Hsf is a substrate of mitogen-activated protein kinase and S378 is the major phosphorylation site. Phosphorylation converts Hsf from a repressor to an activator that works with GAF to activate tll expression. In conclusion, the GAF/Hsf/Ttk69 complex binding to the tor-RE remodels local chromatin structure to repress tll expression and the Tor signaling pathway activate tll expression by modulating a dual transcriptional switch.
Chen
Yu-Chien
YC
Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, 112 Taiwan, ROC.
Lin
Suewei I
SI
Chen
Ying-Kuan
YK
Chiang
Chuen-Sheue
CS
Liaw
Gwo-Jen
GJ
D000818:Animals; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004330:Drosophila / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D005786:Gene Expression Regulation; D000076249:Heat Shock Transcription Factors; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D034622:RNA Interference; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D020218:Response Elements; D012694:Serine / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D000076249:Heat Shock Transcription Factors; C053134:Hsf protein, Drosophila; D012097:Repressor Proteins; C074090:TLL protein, Drosophila; D014157:Transcription Factors; C063460:Trl protein, Drosophila; C075878:ttk protein, Drosophila; D012694:Serine; D020794:Receptor Protein-Tyrosine Kinases; C080148:tor protein, Drosophila; D020928:Mitogen-Activated Protein Kinases; C512966:HDAC1 protein, Drosophila; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases