Garbe J C, Bendena W G, Alfano M, Pardue M L
J Biol Chem. 1986 Dec 25;261(36):16889-94.
Cytological studies have shown that the heat shock loci 93D of Drosophila melanogaster and 2-48B of Drosophila hydei have several characteristics which suggest that they are homologous loci, yet sequence homology is barely detectable by cross-hybridization. Using cloned DNA sequences we have compared the two loci. Both loci produce transcripts of similar size and number. We have characterized the three predominant transcripts. In each species all three transcripts start at or about the same place within the unique portion of the gene. The longest transcript (approximately 9-10 kilobases) continues through several kilobases of short tandem repeats. The two shorter (1.9 and 1.2 kilobases) transcripts terminate 5' to the repeats. The repeat sequences are strongly conserved within a species but between species they have diverged both in length and in sequence. The longest homology is 9 nucleotides. The unique portions have also diverged significantly but do have some regions of conserved sequence. In both species the cytoplasmic transcript is spliced and polyadenylated but does not appear to contain a significant open reading frame. Thus, although the sequence of this locus has diverged significantly there are conserved features which suggest that the function of the locus is also conserved.
细胞学研究表明，黑腹果蝇的热休克基因座93D和海德氏果蝇的2 - 48B具有若干特征，表明它们是同源基因座，但通过杂交几乎检测不到序列同源性。我们使用克隆的DNA序列比较了这两个基因座。两个基因座产生大小和数量相似的转录本。我们对三种主要的转录本进行了表征。在每个物种中，所有三种转录本都在基因独特部分内的同一位置或大致相同位置起始。最长的转录本（约9 - 10千碱基）延伸穿过几千碱基的短串联重复序列。两个较短的转录本（1.9和1.2千碱基）在重复序列的5'端终止。重复序列在一个物种内高度保守，但在不同物种之间，其长度和序列都发生了分歧。最长的同源性为9个核苷酸。独特部分也有显著分歧，但确实存在一些保守序列区域。在两个物种中，细胞质转录本都经过剪接和多聚腺苷酸化，但似乎不包含明显的开放阅读框。因此，尽管该基因座的序列有显著分歧，但仍有保守特征表明该基因座的功能也是保守的。
