昆虫谷胱甘肽S-转移酶的基因结构及其表达调控

谷胱甘肽S-转移酶（glutathione S-transferases, GSTs）属于一个超家族，目前已从20多种昆虫中克隆得到了近百个GSTs基因序列。这些基因分属于至少3个类别，Ⅰ（Delta）类，Ⅱ类和Ⅲ（Epsilon）类，其中Ⅰ类和Ⅲ类是昆虫特异性的类别。昆虫Ⅰ类GSTs基因通常由多基因家族编码，基因多态性在不同昆虫种类中差异很大。Ⅱ类基因的种类较少，基因的结构较简单，通常是单拷贝基因。Ⅲ类基因是最近才鉴定出来的新类别，目前仅在黑腹果蝇和冈比亚按蚊中明确了其在染色体上的定位。基因簇、可变剪接和基因融合等机制是导致昆虫GSTs基因多态性的主要原因。在抗性昆虫种群中，GSTs表达量的增加有mRNA水平的提高和基因扩增两种机制，但后一种机制的报道很少。GSTs活性的增加是由于属于一类或多类的多个同工酶的增量调控，也有少数是由于单个同工酶的增量调控。GSTs的表达受反式调控元件和顺式调控元件的调控。目前仅有少数含有调节基因的染色体大致位点和可能的调控元件得到鉴定。

Gene structure and expression regulation of glutathione S-transferase genes in insects

The glutathione S-transferases (GSTs) belong to a superfamily in which almost 100 sequences have been identified from more than 20 species of insects. All the GST genes belong to at least 3 classes, Ⅰ(Delta) class, Ⅱclass and Ⅲ (Epsilon) class, among which Ⅰand Ⅲ are insect specific class. Genes in GST classⅠare usually encoded by multigene family and the complexity in different species of insects are variable. Fewer genes in GST classⅡare reported; their genomic organization is simple, generally having only one copy. Class Ⅲ are newly identified class and their genomic organization is only clear in Drosophila melanogaster and Anopheles gambiae. Mechanisms of gene cluster, alternative splicing and gene fusion are involved in generating multiple functional GST genes. There are two molecular mechanisms for increased expression of GSTs in resistant insects: elevation in mRNA level and gene amplification while the latter is rarely reported. Elevation of GST activity is involved in upregulation of multiple enzymes belonging to one more GST classes or more rarely upregulation of a single enzyme. The expression is regulated by trans-acting regulators and cis-acting regulating elements. So far only a few crude chromosomal locations which should contain these regulatory genes and some putative regulatory elements have been identified.