A role of polycomb group genes in the regulation of gap gene expression in Drosophila.
Anteroposterior polarity of the Drosophila embryo is initiated by the localized activities of the maternal genes, bicoid and nanos, which establish a gradient of the hunchback (hb) morphogen. nanos determines the distribution of the maternal Hb protein by regulating its translation. To identify further components of this pathway we isolated suppressors of nanos. In the absence of nanos high levels of Hb protein repress the abdomen-specific genes knirps and giant. In suppressor-of-nanos mutants, knirps and giant are expressed in spite of high Hb levels. The suppressors are alleles of Enhancer of zeste (E(z)) a member of the Polycomb group (Pc-G) of genes. We show that E(z), and likely other Pc-G genes, are required for maintaining the expression domains of knirps and giant initiated by the maternal Hb protein gradient. We have identified a small region of the knirps promoter that mediates the regulation by E(z) and hb. Because Pc-G genes are thought to control gene expression by regulating chromatin, we propose that imprinting at the chromatin level underlies the determination of anteroposterior polarity in the early embryo.
Pelegri
F
F
Whitehead Institute, Howard Hughes Medical Institute, Cambridge, Massachusetts.
Lehmann
R
R
D000005:Abdomen; D000483:Alleles; D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics; D004330:Drosophila / Q000196:embryology / Q000235:genetics*; D029721:Drosophila Proteins; D005786:Gene Expression Regulation; D007301:Insect Hormones / Q000235:genetics; D007605:Juvenile Hormones / Q000235:genetics; D009687:Nuclear Proteins; D063151:Polycomb Repressive Complex 2; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000235:genetics*; D016601:RNA-Binding Proteins; D012097:Repressor Proteins / Q000235:genetics; D014157:Transcription Factors
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D007301:Insect Hormones; D007605:Juvenile Hormones; D009687:Nuclear Proteins; D011506:Proteins; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C061245:hb protein, Drosophila; C074089:kni protein, Drosophila; C070574:nos protein, Drosophila; C083329:E(z) protein, Drosophila; D063151:Polycomb Repressive Complex 2