Enhancer traps in the Drosophila bithorax complex mark parasegmental domains.
Eight P elements carrying a beta-galactosidase (lacZ) reporter have been mapped to sites within the Drosophila bithorax complex. The bithorax complex contains three homeotic genes, and at least nine regulatory regions which control their expression in successive parasegments of the fly. The enhancer traps inserted at the promoter of one of the genes, Ultrabithorax, express lacZ in patterns which mimic the Ultrabithorax protein pattern. Enhancer traps in the regulatory regions do not mimic the endogenous genes, but express lacZ globally in the relevant parasegments. Some P elements carry large DNA fragments upstream of the lacZ promoter but internal to the P element. In cases where these internal sequences specify a lacZ pattern, that pattern is generally suppressed when the element is inserted in the bithorax complex. In embryos mutant for genes of the Polycomb group, the lacZ expression from the enhancer traps spreads to all segments. Thus, the enhancer traps reveal parasegmental domains that are maintained by Polycomb-mediated repression. Such domains may be realized by parasegmental differences in chromatin structure.
McCall
K
K
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115.
O'Connor
M B
MB
Bender
W
W
D000818:Animals; D003433:Crosses, Genetic; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D004330:Drosophila / Q000033:anatomy & histology / Q000196:embryology / Q000235:genetics*; D029721:Drosophila Proteins; D004625:Embryo, Nonmammalian; D004742:Enhancer Elements, Genetic; D005260:Female; D015723:Gene Library; D018398:Homeodomain Proteins; D008297:Male; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D015183:Restriction Mapping; D014157:Transcription Factors; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics
D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D014157:Transcription Factors; C066177:Ubx protein, Drosophila; D001616:beta-Galactosidase