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The Torso signaling pathway modulates a dual transcriptional switch to regulate tailless expression.

Chen YC, Lin SI, Chen YK, Chiang CS, Liaw GJ - Nucleic Acids Res. (2009)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, 112 Taiwan, ROC.

ABSTRACT
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.

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A model illustrates how GAF, Hsf and Ttk69 form a repression complex on the tor-RE to initiate tll repression and how the Tor pathway regulates transcriptional switches. Letters A, H, G, R and T inside the cartoons represent activators, Hsf, GAF, co-repressors and Ttk69. Proteins phosphorylated by Mapk are indicated by asterisks.
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Figure 7: A model illustrates how GAF, Hsf and Ttk69 form a repression complex on the tor-RE to initiate tll repression and how the Tor pathway regulates transcriptional switches. Letters A, H, G, R and T inside the cartoons represent activators, Hsf, GAF, co-repressors and Ttk69. Proteins phosphorylated by Mapk are indicated by asterisks.

Mentions: This study showed that the interaction of GAF with Hsf and Ttk69 plays a critical role in regulation of tll expression. At locations where the Tor pathway is inactive, GAF, Hsf, and Ttk69 constitute a protein complex that binds to the tor-RE tightly. The protein complex recruits other co-repressors and chromatin remodeling factors containing Rpd3 to the organization of a high-order local chromatin structure. tll expression is off in this scenario (Figure 7).Figure 7.


The Torso signaling pathway modulates a dual transcriptional switch to regulate tailless expression.

Chen YC, Lin SI, Chen YK, Chiang CS, Liaw GJ - Nucleic Acids Res. (2009)

A model illustrates how GAF, Hsf and Ttk69 form a repression complex on the tor-RE to initiate tll repression and how the Tor pathway regulates transcriptional switches. Letters A, H, G, R and T inside the cartoons represent activators, Hsf, GAF, co-repressors and Ttk69. Proteins phosphorylated by Mapk are indicated by asterisks.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2651784&req=5

Figure 7: A model illustrates how GAF, Hsf and Ttk69 form a repression complex on the tor-RE to initiate tll repression and how the Tor pathway regulates transcriptional switches. Letters A, H, G, R and T inside the cartoons represent activators, Hsf, GAF, co-repressors and Ttk69. Proteins phosphorylated by Mapk are indicated by asterisks.
Mentions: This study showed that the interaction of GAF with Hsf and Ttk69 plays a critical role in regulation of tll expression. At locations where the Tor pathway is inactive, GAF, Hsf, and Ttk69 constitute a protein complex that binds to the tor-RE tightly. The protein complex recruits other co-repressors and chromatin remodeling factors containing Rpd3 to the organization of a high-order local chromatin structure. tll expression is off in this scenario (Figure 7).Figure 7.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, 112 Taiwan, ROC.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus