The sbr gene product in Drosophila melanogaster and its orthologs in yeast(Mex67p) and human (TAP)

A DNA sequence from the 9F region of Drosophila melanogaster polytene chrom osomes was cloned. Sequencing the cloned region and its comparison with the known sequences of the D. melanogaster genome showed that the cloned DNA p art contains gene sbr and adjacent sequences. The literature data on the st ructure and functions of genes TAP in humans and Mex67 in yeast are discuss ed. These genes are orthologous to the sbr gene of Drosophila and control m RNA export from the nucleus to the cytoplasm. The literature evidence is co nsistent with the recessive expression of mutation l(l)ts403 (sbr(10)) upon heat treatment that is manifested as impaired HSP synthesis at the posttra nscriptional level. However, it fails to explain the semidominant effect of the mutation manifested in high frequency of meiotic sex-chromosome nondis junction in heat-treated females. A comparison of amino-acid sequences corr esponding to the products of the three orthologous genes, TAP, Mex67, and s br, showed that the sbr gene product of Drosophila is more similar to the h uman TAP factor than to the Mex67 factor in yeast.