white+ transgene insertions presenting a dorsal/ventral pattern define a single cluster of homeobox genes that is silenced by the polycomb-group proteins in Drosophila melanogaster.
We used the white gene as an enhancer trap and reporter of chromatin structure. We collected white+ transgene insertions presenting a peculiar pigmentation pattern in the eye: white expression is restricted to the dorsal half of the eye, with a clear-cut dorsal/ventral (D/V) border. This D/V pattern is stable and heritable, indicating that phenotypic expression of the white reporter reflects positional information in the developing eye. Localization of these transgenes led us to identify a unique genomic region encompassing 140 kb in 69D1-3 subject to this D/V effect. This region contains at least three closely related homeobox-containing genes that are constituents of the iroquois complex (IRO-C). IRO-C genes are coordinately regulated and implicated in similar developmental processes. Expression of these genes in the eye is regulated by the products of the Polycomb-group (Pc-G) and trithorax-group (trx-G) genes but is not modified by classical modifiers of position-effect variegation. Our results, together with the report of a Pc-G binding site in 69D, suggest that we have identified a novel cluster of target genes for the Pc-G and trx-G products. We thus propose that ventral silencing of the whole IRO-C in the eye occurs at the level of chromatin structure in a manner similar to that of the homeotic gene complexes, perhaps by local compaction of the region into a heterochromatin-like structure involving the Pc-G products.
Netter
S
S
Embryologie Moléculaire et Expérimentale-Centre National de la Recherche Scientifique/Unité de Recherche Associée 2227, Université Paris Sud, 91405 Orsay Cedex, France.
Fauvarque
M O
MO
Diez del Corral
R
R
Dura
J M
JM
Coen
D
D
D018528:ATP-Binding Cassette Transporters; D000818:Animals; D019521:Body Patterning / Q000235:genetics*; D002478:Cells, Cultured; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins / Q000235:genetics; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics*; D005127:Eye Color / Q000235:genetics; D005136:Eye Proteins / Q000235:genetics*; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics; D019476:Insect Proteins / Q000235:genetics*; D008957:Models, Genetic; D063150:Polycomb Repressive Complex 1; D012097:Repressor Proteins / Q000235:genetics*; D014157:Transcription Factors; D019076:Transgenes
C099257:ARA protein, Drosophila; D018528:ATP-Binding Cassette Transporters; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; D019476:Insect Proteins; C066770:Pc protein, Drosophila; D012097:Repressor Proteins; D014157:Transcription Factors; C063460:Trl protein, Drosophila; C099258:caup protein, Drosophila; C059254:w protein, Drosophila; D063150:Polycomb Repressive Complex 1