A conserved regulatory element present in all Drosophila rhodopsin genes mediates Pax6 functions and participates in the fine-tuning of cell-specific expression.
The Drosophila rhodopsin genes (rh's) represent a unique family of highly regulated cell-specific genes, where each member has its own expression pattern in the visual system. Extensive analysis of the rh's has revealed several functional elements that are involved in cell-specificity. We have investigated the functional role of the RCSI/P3 site that is found in the proximal promoter of all Drosophila rh genes. This sequence is remarkably conserved in evolution and is located 15-30 bp upstream of the TATA box. We have previously shown that, in the context of the rh1 promoter, this element is recognized in vivo by a Pax6 protein, the master regulator of eye development. Thus, rh regulation might represent the ancestral function of Pax6. Here, we investigated the role of the RCSI/P3 sequence in the other rh genes and show that they also mediate Pax6 function. We also tested the potential impact of the various RCSI/P3 sequences on the precise cell-specific expression of rh genes. Our results demonstrate that, even though all RCSI/P3 sequences bind Pax6, they are clearly distinct in various rh promoters and these differences are conserved throughout evolution: RCSI/P3 appears to participate in the fine-tuning of cell-specificity. We also show that Pax6 or a related Pax protein may be involved in the regulation of olfactory genes. Therefore, in addition to performing a global photoreceptor-specific function, RCSI also appears to mediate the combined action of Pax6 and other factors and to contribute to rh regulation in subsets of photoreceptors.
Laboratory of Molecular Genetics, Department of Biology, New York University, 1009 Main Building, 100 Washington Square East, New York, NY 10003, USA.
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Papatsenko
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Nazina
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Desplan
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017124:Conserved Sequence; D004330:Drosophila / Q000196:embryology* / Q000235:genetics; D005136:Eye Proteins; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016296:Mutagenesis; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins; D012243:Rhodopsin / Q000096:biosynthesis / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D019076:Transgenes
D005136:Eye Proteins; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D012243:Rhodopsin