Thackeray J R, Ganetzky B
Laboratory of Genetics, University of Wisconsin, Madison 53706, USA.
Genetics. 1995 Sep;141(1):203-14. doi: 10.1093/genetics/141.1.203.
We cloned genomic DNA corresponding to the Drosophila virilis homologue of para, a gene encoding a sodium channel alpha-subunit, and obtained many partial cDNA clones from embryos and adults. Para protein has been well conserved, and the optional elements at six different sites of alternative splicing in D. melanogaster are present in D. virilis, in addition to one new optional exon. Among 31 different splice-types observed in D. virilis, the stage-specific pattern of alternative splicing seen in D. melanogaster is also conserved. Comparison of genomic DNA sequence revealed three aspects that vary between alternatively and constitutively used exon sequences. Sixteen short blocks (10-75 bp), the only recognizably conserved intron sequence, were disproportionately associated with alternatively used splice sites. Silent site substitutions were found much less frequently in alternative than constitutive exon elements, and the degree of match to the Drosophila splice site consensus tended to be lower at less frequently selected alternative splice junctions. This study shows that the developmentally regulated variability of para products is highly conserved and therefore likely to be of functional significance and suggests that a variety of different sequence-dependent mechanisms may regulate this pattern of alternative splicing.
我们克隆了与果蝇para基因的果蝇virilis同源物相对应的基因组DNA，para基因编码一种钠通道α亚基，并从胚胎和成虫中获得了许多部分cDNA克隆。Para蛋白一直高度保守，除了一个新的可变外显子外，果蝇melanogaster中六个不同可变剪接位点的可选元件在果蝇virilis中也存在。在果蝇virilis中观察到的31种不同剪接类型中，果蝇melanogaster中出现的阶段特异性可变剪接模式也得到了保守。基因组DNA序列的比较揭示了可变和组成性使用的外显子序列之间存在差异的三个方面。16个短片段（10 - 75 bp）是唯一可识别的保守内含子序列，与可变使用的剪接位点不成比例地相关。在可变外显子元件中，沉默位点替换的频率远低于组成性外显子元件，并且在较少选择的可变剪接连接处，与果蝇剪接位点共有序列的匹配程度往往较低。这项研究表明，para产物的发育调控变异性高度保守，因此可能具有功能意义，并表明多种不同的序列依赖性机制可能调节这种可变剪接模式。
