Repression by TTK69 of GAGA-mediated activation occurs in the absence of TTK69 binding to DNA and solely requires the contribution of the POZ/BTB domain of TTK69.
tramtrack 69 (TTK69) is known to repress GAGA-mediated activation of the eve promoter in S2 cells. Here, we show that repression by TTK69 occurs in the absence of bona fide TTK69-binding sites on the template, indicating that it does not require the binding of TTK69 to DNA. Consistent with this interpretation, the POZ/BTB domain of TTK69, which does not bind DNA, is sufficient for repression. Moreover, a fusion protein in which the POZ/BTB domain of GAGA is replaced by that of TTK69 is not capable of activating the eve promoter but efficiently represses GAGA-dependent activation. Repression involves GAGA-TTK69 interaction because TTK69 is not capable of repressing basal transcription. Most probably, GAGA-TTK69 interaction occurs at the promoter because GAGA.TTK69 complexes are fully competent in binding DNA in vitro. Our results also show that repression by TTK69 of GAGA-dependent activation of the eve promoter is not mediated by any of the co-repressors known to interact with TTK69 (dMi2 or C-terminal binding protein) or by trichostatin A-sensitive histone deacetylases. Altogether, these observations strongly suggest that the binding of TTK69 prevents the interaction of GAGA with the transcription machinery and, therefore, compromises its activation potential.
Pagans
Sara
S
Department de Biologia Molecular i Cellular, Institut de Biologia Molecular de Barcelona, Consejo Superior de Investigaciones Científicas, Jordi Girona Salgado, 18-26, 08034 Barcelona, Spain.
Piñeyro
David
D
Kosoy
Ana
A
Bernués
Jordi
J
Azorín
Fernando
F
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins; D003850:Deoxyribonuclease I / Q000378:metabolism; D004330:Drosophila; D029721:Drosophila Proteins; D006655:Histone Deacetylases / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism*; D006877:Hydroxamic Acids / Q000494:pharmacology; D008954:Models, Biological; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D006877:Hydroxamic Acids; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C063460:Trl protein, Drosophila; C075878:ttk protein, Drosophila; C012589:trichostatin A; D004247:DNA; D003850:Deoxyribonuclease I; D006655:Histone Deacetylases