No abstract

The major heat shock protein of 70,006 M, in Drosophila melanogaster is encoded by two variant gene types located, respectively, at the chromosomal sites 8787 and 87Cl. We present the DNA sequence of a complete hsp70t gene of the 87A7 type and of the adjacent regions from both variants, extending to 1.2 x 10' bases upstream from the start of the messenger coding region. We find an untranslated region of 250 nucleotides at the 5' end of the messenger coding sequence in both variants. There is only one open reading frame which allows coding of a 70,000 M, protein within the 8787 variant, as found for an 87Cl variant (Ingolia et al., 1980). We observe 4.2?6 nucleotide divergence between these two variants with complete conservation of the reading frame. There is a conserved sequence of 355 nucleotides in front of each hap70 gene, which is 85% homologous between the two variants. The presence of the same sequence element in y, in front of the @ heat shock genes (R. W. Hackett & J. T. Lis, personal communication) suggests that this element contains the regulatory signals for the coordinate expression of both the hsp70 and the + heat shock genes. Finally we find a very A+T-rich sequence of 150 basepairs which is highly conserved (91.87;) @6 x lo3 bases upstream from two hps70 gene variants.

Abstract. The tumor suppressor gene overgrown hematopoietic organs-31 (oho31) of Drosophila encodes a protein with extensive homology to the Importin protein of Xenopus (50% identity), the related yeast SRP1 protein, and the mammalian hSRP1 and RCH1 proteins. A strong reduction in the expression of oho31 by a P element inserted in the 5' untranslated region of the oho31 transcript or a complete inactivation of oho31 by imprecise P element excision leads to malignant development of the hematopoietic organs and the genital disc, as shown by their growth autonomy in transplantation assays. We have cloned the oho31 gene of Drosophila melanogaster and determined its nucleotide sequence. The gene encodes a phosphoprotein of 522 amino acids made of three domains: a central hydrophobic domain of eight repeats of 42-44 amino acids each, displaying similarity to the arm motif found in junctional and nucleopore complex proteins, and flanked by two hydrophilic NH2-and COOH-terminal domains. Immunostaining revealed that the 0H031 protein is supplied maternally and rapidly degraded during the first 13 nuclear divisions. Thereafter, the 0H031 protein is predominantly expressed, albeit at reduced levels, in proliferating tissues. During the interphase of early embryonic cell cycles, the 0H031 protein is present in the cytoplasm and massively accumulates in the nucleus at the onset of mitosis in late interphase and prophase. The nuclear import of 0H031 is, however, less pronounced during later developmental stages. These results suggest that, similar to Importin, 0H031 may act as a cytosolic factor in nuclear transport. Moreover, the cell cycle-dependent accumulation of 0H031 in the nucleus indicates that this protein may be required for critical nuclear reactions occurring at the onset of mitosis.