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Insect Biochem Mol Biol. 2001 Nov 1;31(12):1201-11.

The mechanism of sex-specific splicing at the doublesex gene is different between Drosophila melanogaster and Bombyx mori.

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Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, 113-8657, Tokyo, Japan.


We have previously reported that Bmdsx, a homologue of the sex-determining gene, doublesex (dsx), was found to be sex-specifically expressed in various tissues at larval, pupal, and adult stages in the silkworm, Bombyx mori, and was alternatively spliced to yield male- and female-specific mRNAs. To reveal sex-specific differences in splicing patterns of Bmdsx pre-mRNA, the genomic sequence was determined and compared with male- and female-specific Bmdsx cDNA sequences. The open reading frame (ORF) consisted of five exons. Exons 3 and 4 were specifically incorporated into the female type of Bmdsx mRNA. On the other hand, exon 2 was spliced to exon 5 to produce the male type mRNA of Bmdsx. As in the case of Drosophila dsx, the OD2 domain was separated by a female-specific intron into sex-independent and sex-dependent regions. Sex-specific splicing occurred in equivalent positions in the Drosophila dsx gene. However, unlike Drosophila dsx, the female-specific introns showed no weak 3' splice sites, and the TRA/TRA-2 binding site related sequences were not found in the female-specific exon, nor even in any other regions of the Bmdsx gene. Moreover, an in vitro splicing reaction consisting of HeLa cell nuclear extracts showed that the female-type of Bmdsx mRNA represented the default splicing. These findings suggest that the structural features of the sex-specific splicing patterns of Bmdsx pre-mRNA are similar to those of Drosophila dsx but the regulation of sex-specific alternative splicing of Bmdsx pre-mRNA is different.

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