Russell S R, Kaiser K
Department of Genetics, University of Glasgow, Scotland.
Genetics. 1993 May;134(1):293-308. doi: 10.1093/genetics/134.1.293.
We have identified of set of related transcripts expressed in the germ line of male Drosophila melanogaster. Surprisingly, while one of the corresponding genes is autosomal the remainder are located on the Y chromosome. The autosomal locus, at 77F on chromosome arm 3L, corresponds to the previously described transcription unit 18c, located in the first intron of the gene for an RI subunit of cAMP-dependent protein kinase. The Y chromosome copies have been mapped to region h18-h19 on the cytogenetic map of the Y outside of any of the regions required for male fertility. In contrast to D. melanogaster, where Y-linked copies were found in nine different wild-type strains, no Y-linked copies were found in sibling species. Several apparently Y-derived cDNA clones and one Y-linked genomic clone have been sequenced. The Y-derived genomic DNA shares the same intron/exon structure as the autosomal copy as well as related flanking sequences suggesting that it transposed to the Y from the autosomal locus. However, this particular Y-linked copy cannot encode a functional polypeptide due to a stop codon at amino acid position 72. Divergence among five different cDNA clones ranges from 1.5 to 6% and includes a large number of third position substitutions. We have not yet obtained a full-length cDNA from a Y-linked gene and therefore cannot conclude that the D. melanogaster Y chromosome contains functional protein-coding genes. The autosomal gene encodes a predicted polypeptide with 45% similarity to histones of the H5 class and more limited similarity to cysteine-rich protamines. This protein may be a distant relative of the histone H1 family perhaps involved in sperm chromatin condensation.
我们已经鉴定出一组在雄性黑腹果蝇生殖系中表达的相关转录本。令人惊讶的是，虽然其中一个相应基因是常染色体的，但其余基因位于Y染色体上。位于3L染色体臂77F处的常染色体基因座对应于先前描述的转录单位18c，它位于cAMP依赖性蛋白激酶RI亚基基因的第一个内含子中。Y染色体上的拷贝已被定位到Y染色体细胞遗传图谱上的h18 - h19区域，该区域不在雄性生育所需的任何区域内。与在九个不同野生型菌株中发现Y连锁拷贝的黑腹果蝇不同，在其近缘物种中未发现Y连锁拷贝。已经对几个明显源自Y染色体的cDNA克隆和一个Y连锁基因组克隆进行了测序。源自Y染色体的基因组DNA与常染色体拷贝具有相同的内含子/外显子结构以及相关的侧翼序列，这表明它是从常染色体基因座转座到Y染色体上的。然而，由于在氨基酸位置72处存在终止密码子，这个特定的Y连锁拷贝不能编码功能性多肽。五个不同cDNA克隆之间的差异范围为1.5%至6%，包括大量第三位替换。我们尚未从Y连锁基因获得全长cDNA，因此不能得出黑腹果蝇Y染色体包含功能性蛋白质编码基因的结论。常染色体基因编码一种预测的多肽，与H5类组蛋白有45%的相似性，与富含半胱氨酸的鱼精蛋白的相似性较低。这种蛋白质可能是组蛋白H1家族的远亲，可能参与精子染色质凝聚。
