中文摘要：

在PRRSV感染性克隆pCBC2的基础上，通过突变PCR获得了病毒基因组5’UTR系列缺失的全长突变体克隆：pCBCM1、pCBCM3、pCBCM5、pCBCM7、pCBCM9、pCBCM45、pCBCM69、pCBCM100，随后将上述突变体体外转录成RNA之后转染MARC-145细胞，进行病毒感染性、复制和转录分析，以鉴定特定的缺失区的调控功能。结果显示，病毒5’UTR起始的第1个碱基是保持病毒感染性非必需的核苷酸；前45个碱基对病毒基因组的复制是非必需的。Northern—Blot结果显示pCBCM1亚基因组mRNA可以进行高效率的转录，而其余突变体的亚基因组转录受到严重抑制。由此证明，PRRSV5’UTR的完整性对病毒意义重大，碱基的少量以及大部分缺失会对病毒产生极大的影响。

英文摘要：

The genomic 5＇ untranslated region （UTR） of single-stranded,positive-sense RNA viruses is thought to play a very important role in viral genomic replication,subgenomic mRNA transcription and protein translation. In this study,based on the porcine reproductive and respiratory syndrome virus （PRRSV） infectious full length eDNA elone pCBC2,a series of eDNA clones with 5＇ UTR truncated were obtained through PCR-based mutagenesis. Then the RNAs via in vitro transcription were respectively transfected into MARC-145 cells for further cytopathie effect （CPE） observation,genomic and subgenomic mRN A analysis,to investigate the regulatory function of 5＇ UTR. Results showed that the first base pair of PRRSV 5＇ UTR should be dispensable for the virus infection; the 45bp in 5＇ end of 5＇ UTR was dispensable for genomic RNA replication but those mutants truncated in this region couldn＇t cause CPE. The results mentioned above indicated that the integrity of 5＇ UTR should be crucial for the replication and transcription of PRRSV.