EXPRESSION OF DROSOPHILA GLASS PROTEIN AND EVIDENCE FOR NEGATIVE REGULATION OF ITS ACTIVITY IN NONNEURONAL CELLS BY ANOTHER DNA-BINDING PROTEIN

The glass gene encodes a DNA-binding zinc-finger protein required for the development of Drosophila photoreceptor cells and which appears to regulate a number of genes specifically expressed in photoreceptors. We have generated monoclonal antibodies to Glass and used them to exam ine Glass distribution during development. Glass is expressed in all c ell types of the developing eye and in all other organs that contain p hotoreceptor cells in Drosophila, including a small number of cells in the brain. We altered the normal pattern of glass expression by placi ng the gene under the control of the hsp70 promoter. Our results sugge st that nonphotoreceptor cells are restricted in their response to Gla ss expression. In an effort to discover the mechanism of this restrict ion, we examined the expression of a number of reporter gene construct s. Our results suggest that nonsensory cells are unable to express cer tain reporter constructs in response to Glass expression because anoth er DNA-binding factor represses Glass activity in nonsensory cells.