A SEQUENCE CONSERVED IN VERTEBRATE HOX GENE INTRONS FUNCTIONS AS AN ENHANCER REGULATED BY POSTERIOR HOMEOTIC GENES IN DROSOPHILA IMAGINAL DISCS

The intron of the mouse Hoxa-4 gene acts as a strong homeotic response element in Drosophila melanogaster leg imaginal discs. This activity depends on homeodomain binding sites present within a 30 bp conserved element, HB1, in the intron. A similar arrangement of homeodomain bind ing sites is found in many other potential homeotic target genes. HB1 activity in Drosophila imaginal discs is activated by Antennapedia and more posterior homeotic genes, but is not activated by more anterior genes, Testing a reporter gene construct with mutated binding sites in mouse embryos shows that HB1 is also active in the expression domains of posterior Hax genes in the mouse neural tube. (C) 1997 Elsevier Sc ience Ireland Ltd.