Developmental regulation and complex organization of the promoter of the non-coding hsrω gene of Drosophila melanogaster

Abstract

The nucleus-limited large non-coding hsrω-n RNA product of the93D or the hsrω gene of Drosophila melanogaster binds to a variety of RNA-binding proteins involved in nuclear RNA processing. We examined the developmental and heat shock induced expression of this gene by in situ hybridization of nonradioactively labelled riboprobe to cellular transcripts in intact embryos, larval and adult somatic tissues of wild type and an enhancer-trap line carrying the hsrω⁰⁵²⁴¹ allele due to insertion of aP-LacZ-rosy + transposon at - 130 bp position of the hsrω promoter. We also examined LacZ expression in the enhancer-trap line and in two transgenic lines carrying different lengths of the hsrω promoter upstream of the LacZ reporter. The hsrΩ gene is expressed widely at all developmental stages; in later embryonic stages, its expression in the developing central nervous system was prominent. In spite of insertion of a big transposon in the promoter, expression of the hsrω⁰⁵²⁴¹ allele in the enhancer-trap line, as revealed byin situ hybridization to hsrω transcripts in cells, was similar to that of the wild type allele in all the embryonic, larval and adult somatic tissues examined. Expression of the LacZ gene in this enhancer-trap line was similar to that of the hsrω RNA in all diploid cell types in embryos and larvae but in the polytene cells, the LacZ gene did not express at all, neither during normal development nor after heat shock. Comparison of the expression patterns of hsrω gene and those of the LacZ reporter gene under its various promoter regions in the enhancer-trap and transgenic lines revealed a complex pattern of regulation, which seems to be essential for its dynamically varying expression in diverse cell types.