应用果蝇yellow基因的分子模式分析基因转应作用(英文)

基因转应作用（ｔｒａｎｓｖｅｃｔｉｏｎ）是基因表达的一种方式，这种方式是由等位基因配对及其相互作用所介导的。基因转应作用的现象已在果蝇的多种基因中发现。这种作用可产生正负两种效应。而且，在其它物种中，也逐渐发现了类似的现象。例如，在植物中的基因沉默现象（ｇｅｎｅｓｉｌｅｎｃｉｎｇ）以及在小鼠中的基因转激活作用（ｔｒａｎｓａｃｔｉｖａｔｉｏｎ）等。因此，阐明基因转应作用的机理，将有助于了解基因表达调节及增强子调控活动的分子基础。本文应用果蝇ｙｅｌｏｗ基因为模式来探讨基因转应作用的分子机制。前期研究表明，ｙｅｌｏｗ基因转应作用发生于ｇｙｐｓｙ诱导的ｙ２突变种和ｙｅｌｏｗ亚等位基因（ｙｈ）之间。为了证实是否ｇｙｐｓｙ是基因转应作用所必需的ＤＮＡ元件，我们鉴定了一种新的ｙｅｌｏｗ突变种，称为ｙ２３７４。ｙ２３７４突变是一种基因表达的组织特异性改变，这一改变使ｙ２３７４果蝇在翅和身体部位表皮着色呈突变型。通过遗传分析表明，ｙ２３７４也可与ｙｈ（如ｙ１＃８）产生基因转应作用。ｙ１＃８是一种无效的ｙｅｌｏｗ等位基因，它包含一个启动子和部分编码区序列的缺失。然而，当ｙ２３７４与ｙ１＃８杂交后，其杂交后代的表现型可由ｙ２３７

Molecular Analysis of Gene Transvection by Using Drosophila yellow Gene Model 1

Transvection is a form of pairing modulated gene expression. These effects can be positive or negative and are seen at a large number of genes. We are investigating the molecular basis of transvection at the yellow gene of Drosophila. All previous studies of transvection involved complementation between the gypsy induced y 2 mutation and certain yellow hypomorphic alleles ( y h ). To determine whether gypsy was essential for transvection, we examined a new yellow allele, y 2374 , which is a mutant in wing and body pigmentation. However, pairing of the y 2374 allele with some y h alleles results in progeny with wild type in these tissues, suggesting that y 2374 can transvect y h alleles. The molecular characterization shows that y 2374 mutation is not caused by gypsy element, demonstrating that gene transvection does not require this transposable element. Furthermore, we found that y 2374 mutation was caused by a large insertion into the yellow gene between the wing and body enhancers and promoter. This result suggests that enhancers of yellow gene may not act from long distance on the promoter.