杆状病毒基因前导小顺反子的序列特征及其翻译衰减调控模型

PROPERTIES OF THE LEADING MINI CISTRON OF BACULOVIRUS GENE AND A TRANSLATION ATTENUATING REGULATION MODEL

在杆状病毒许多基因的ｍＲＮＡ前导序列中存在一类小顺反子（Ｍｉｎｉｃｉｓｔｒｏｎ）结构．发现某些昆虫基因和苜蓿尺蠖核型多角体病毒的基因在密码子的使用偏向上各不相同．而小顺反子一般偏向于使用少数密码子，具有重复密码子．小顺反子与大顺反子同框；多数小顺反子的ＡＴＧ上下游符合Ｋｏｚａｋ序列；有的小顺反子起始密码子后紧跟着就是终止密码子．这些特征暗示小顺反子可能是一类独特的有别于其它杆状病毒基因而具有特殊功能的“基因”．小顺反子的作用可能与原核生物氨基酸衰减调控子Ａｔｅｎｕａｔｏｒ有相似之处，但它不是在转录水平，而在翻译水平上减弱其后大顺反子的表达．

Mini cistrons are present in the mRNA leading regions of some baculoviral genes. By analyzing the codon usage of insect genes,the early, late and polyhedrin genes and mini cistrons of baculovirus ,it is found that mini cistrons prefer minor codons to major codons that are rich in polyhedrin genes; have repeat codons whose content is 250 times very higher than in the polyhedrin genes;almost all mini cistrons are inframe with the succeeding major cistrons; and most ATG of mini cistrons are in good context for translation.All above suggest that the mini cistrons are a distinct kind of gene which has particular function. In this paper, it is proposed that the function of mini cistron may be similar to that of attenuator, namely attenuating or stutting off translation of the succeeding major cistron under the condition of low amino tRNA. \ \