Ovarian follicle cell enhancers from the Drosophila yolk protein genes: different segments of one enhancer have different cell-type specificities that interact to give normal expression.

This paper examines ovarian transcription of the divergently oriented yolk protein genes 1 and 2 (yp1 and yp2) of Drosophila melanogaster. We report germ line transformation results demonstrating that yp1 and yp2 are transcribed in the same subpopulations of ovarian follicle cells. Our results show that this expression pattern is directed by two enhancers: ovarian enhancer 1, located between the genes, and ovarian enhancer 2, located within the first exon of yp2. Analysis of the expression pattern resulting from alterations in ovarian enhancer 1 demonstrates that different segments of this enhancer have different positive or negative effects on the cell-type specificity of transcription.