家蚕传染性软化病病毒(桐乡株)5′端非编码区基因的克隆及序列分析

Cloning and Sequence Analysis of 5′ Non-coding Region of Bombyx mori Infectious Flacherie Virus Isolated in Tongxiang,China

为了探讨家蚕传染性软化病病毒的复制与翻译机制,利用cDNA 5′末端快速扩增(5′-RACE)技术获得了家蚕传染性软化病病毒桐乡分离株(Bombyxmoriinfectious flacherie virus,BmIFV-2)的5′端非编码区(non-coding region,NCR)。序列比较分析发现:BmIFV-2的5′-NCR由155个核苷酸组成,A+U含量达60.64%,其中包含1个起始密码子AUG;与坂城分离株(BmIFV-1)的5′-NCR相比,BmIFV-2的5′-NCR在5′末端缺少1个核苷酸,但核苷酸识别率为100%(即单核苷酸变异率为0),而且这个缺少的核苷酸并不影响其5′-NCR的二级结构。与已经证实具有内部核糖体进入位点(internal ribosome entry site,IRES)活性的Iflavirus属的2种病毒EoPV(Ectropis obliquapicor-na-like virus)和VDV-1(Varroa destructorvirus 1)的5′-NCR相比,BmIFV的5′-NCR可能也具有IRES活性。

In this study, the 5＇ non-coding region （NCR） of Bombyx mori infectious flacherie virus isolated in Tongxiang, China （BmlFV-2） was obtained through 5＇-RACE. Sequence analysis revealed that BmlFV-2 has 155 nucleotides in its 5＇-NCR, which contains an AUG, and the content of A ＋U reaches 60.64%. Although the 5＇-NCR of BmlFV-2 was one nucleotide shorter than that of the strain isolated in Japan （ BmlFV-1 ）, the nu- cleotide recognition ratio was 100% （i. e., no single-nucleotide polymorphism）. In addition, the absent nucleotide did not affect the secondary structure of 5＇-NCR. Sequence comparison with 5＇-NCR of two viruses, EoPV and VDV-1 from genus Iflavirus, indicated that the 5＇-NCR of BmtFV might have IRES （internal ribosome entry site） activity as these two viruses.