Kurek R, Reugels A M, Glätzer K H, Bünemann H
Dipartimento di Genetica e Biologia Molecolare, Universita di Roma 'La Sapienza,' I-00185 Roma, Italia.
Genetics. 1998 Jul;149(3):1363-76. doi: 10.1093/genetics/149.3.1363.
To understand the contradiction between megabase-sized lampbrush loops and putative protein encoding genes both associated with the loci of Y chromosomal fertility genes of Drosophila on the molecular level, we used PCR-mediated cloning to identify and isolate the cDNA sequence of the Y chromosomal Drosophila hydei gene DhDhc7(Y). Alignment of the sequences of the putative protein DhDhc7(Y) and the outer arm dynein beta heavy chain protein DYH2 of Tripneustes gratilla shows homology over the entire length of the protein chains. Therefore the proteins can be assumed to fulfill orthologous functions within the sperm tail axonemes of both species. Functional dynein beta heavy chain molecules, however, are necessary for the assembly and attachment of outer dynein arms within the sperm tail axoneme. Localization of DhDhc7(Y) to the fertility factor Threads, comprising at least 5.1 Mb of transcriptionally active repetitive DNA, results from an infertile Threads- mutant where large clusters of Threads specifically transcribed satellites and parts of DhDhc7(Y) encoding sequences are missing simultaneously. Consequently, the complete lack of the outer dynein arms in Threads- males most probably causes sperm immotility and hence infertility of the fly. Moreover, preliminary sequence analysis and several other features support the hypothesis that DhDhc7(Y) on the lampbrush loops Threads in D. hydei and Dhc-Yh3 on the lampbrush loops kl-5 in Drosophila melanogaster on the heterochromatic Y chromosome of both species might indeed code for orthologous dynein beta heavy chain proteins.
为了在分子水平上理解与果蝇Y染色体育性基因位点相关的兆碱基大小的灯刷环和假定的蛋白质编码基因之间的矛盾，我们使用PCR介导的克隆来鉴定和分离果蝇海德氏Y染色体基因DhDhc7(Y)的cDNA序列。假定的蛋白质DhDhc7(Y)与海胆的外臂动力蛋白β重链蛋白DYH2的序列比对显示，在蛋白质链的全长上具有同源性。因此，可以假定这两种蛋白质在两个物种的精子尾轴丝中发挥直系同源功能。然而，功能性动力蛋白β重链分子对于精子尾轴丝中外动力蛋白臂的组装和附着是必需的。DhDhc7(Y)定位于育性因子Threads，Threads包含至少5.1 Mb的转录活性重复DNA，这是由于一个不育的Threads突变体导致的，在该突变体中，大量特定转录的Threads卫星簇和部分DhDhc7(Y)编码序列同时缺失。因此，Threads雄性中完全缺乏外动力蛋白臂很可能导致精子运动能力丧失，进而导致果蝇不育。此外，初步序列分析和其他几个特征支持这样的假设，即海德氏果蝇灯刷环Threads上的DhDhc7(Y)和黑腹果蝇异染色质Y染色体上灯刷环kl-5上的Dhc-Yh3可能确实编码直系同源的动力蛋白β重链蛋白。
