Zeste maintains repression of Ubx transgenes: support for a new model of Polycomb repression.
During late embryogenesis, the expression domains of homeotic genes are maintained by two groups of ubiquitously expressed regulators: the Polycomb repressors and the Trithorax activators. It is not known how the activities of the two maintenance systems are initially targeted to the correct genes. Zeste and GAGA are sequence-specific DNA-binding proteins previously shown to be Trithorax group activators of the homeotic gene Ultrabithorax (Ubx). We demonstrate that Zeste and GAGA DNA-binding sites at the proximal promoter are also required to maintain, but not to initiate, repression of UBX: Furthermore, the repression mediated by Zeste DNA-binding site is abolished in zeste null embryos. These data imply that Zeste and probably GAGA mediate Polycomb repression. We present a model in which the dual transcriptional activities of Zeste and GAGA are an essential component of the mechanism that chooses which maintenance system is to be targeted to a given promoter.
Hur
Man-Wook
MW
Department of Biochemistry and Molecular Biology, Yonsei University School of Medicine, 134 ShinChon-Dong, SeoDaeMoon-Ku, Seoul, Korea 120-752.
Laney
Jeffrey D
JD
Jeon
Sang-Hack
SH
Ali
Janann
J
Biggin
Mark D
MD
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics*; D004330:Drosophila / Q000196:embryology / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics; D019476:Insect Proteins / Q000235:genetics*; D063150:Polycomb Repressive Complex 1; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D019476:Insect Proteins; C066770:Pc protein, Drosophila; D012097:Repressor Proteins; D014157:Transcription Factors; C063460:Trl protein, Drosophila; C066177:Ubx protein, Drosophila; C060849:z protein, Drosophila; D063150:Polycomb Repressive Complex 1