Discrete Polycomb-binding sites in each parasegmental domain of the bithorax complex.
The Polycomb protein of Drosophila melanogaster maintains the segmental expression limits of the homeotic genes in the bithorax complex. Polycomb-binding sites within the bithorax complex were mapped by immunostaining of salivary gland polytene chromosomes. Polycomb bound to four DNA fragments, one in each of four successive parasegmental regulatory regions. These fragments correspond exactly to the ones that can maintain segmentally limited expression of a lacZ reporter gene. Thus, Polycomb acts directly on discrete multiple sites in bithorax regulatory DNA. Constructs combining fragments from different regulatory regions demonstrate that Polycomb-dependent maintenance elements can act on multiple pattern initiation elements, and that maintenance elements can work together. The cooperative action of maintenance elements may motivate the linear order of the bithorax complex.
Chiang
A
A
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
O'Connor
M B
MB
Paro
R
R
Simon
J
J
Bender
W
W
D000818:Animals; D002874:Chromosome Mapping; D004247:DNA; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics*; D015870:Gene Expression; D005801:Genes, Homeobox; D007301:Insect Hormones / Q000235:genetics*; D009024:Morphogenesis / Q000235:genetics; D063150:Polycomb Repressive Complex 1; D011506:Proteins / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D012469:Salivary Glands / Q000502:physiology
D029721:Drosophila Proteins; D007301:Insect Hormones; C066770:Pc protein, Drosophila; D011506:Proteins; D004247:DNA; D063150:Polycomb Repressive Complex 1