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

The nucleus-limited large non-coding hsr omega -n RNA product of the 93D or the hsr omega gene of Drosophila melanogaster binds to a variety of RNA-bi nding proteins involved in nuclear RNA processing. We examined the developm ental and heat shock induced expression of this gene by in situ hybridizati on of nonradioactively labelled riboprobe to cellular transcripts in intact embryos, larval and adult somatic tissues of wild type and an enhancer-tra p line carrying the hsr omega (05241) allele due to insertion of a P-LacZ-r osy(+) transposon at - 130 bp position of the hsr omega promoter. We also e xamined LacZ expression in the enhancer-trap line and in two transgenic lin es carrying different lengths of the hsr omega promoter upstream of the Lac Z reporter. The hsr omega gene is expressed widely at all developmental sta ges; in later embryonic stages, its expression in the developing central ne rvous system was prominent. In spite of insertion of a big transposon in th e promoter, expression of the hsr omega (05241) allele in the enhancer-trap line, as revealed by in situ hybridization to hsr omega transcripts in cel ls, was similar to that of the wild type allele in all the embryonic, larva l and adult somatic tissues examined. Expression of the LacZ gene in this e nhancer-trap line was similar to that of the hsr omega RNA in all diploid c ell types in embryos and larvae but in the polytene cells, the LacZ gene di d not express at all, neither during normal development nor after heat shoc k. Comparison of the expression patterns of hsr omega 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 typ es.