Ⅰ型马立克氏病强弱毒株Meq基因的克隆与序列分析

目的]为获得MDV-1强弱毒株Meq基因序列的差异。方法]根据GENE BANK登录的马立克氏病毒Meq基因序列，设计一对引物，采用PcR技术对MDV—Ⅰ型国内商用CVI988／Rispens疫苗株和参考强毒京-1（BJ-1）株的Meq基因进行了扩增，并将扩增产物提纯后克隆到pcDNA3．1（＋）上，进行酶切鉴定及测序验证。结果]CVI988疫苗株和BJ-1强毒株的Meq基因开放阅读框（ORF）长度分别为1200和1197bp。通过与国际标准强毒GA株Meq基因进行比较，BJ-1株和CVI988株Meq基因中分别有一段180和177bp的插入序列，第211住核苷酸由G变为T，导致第71位氨基酸由丙氨酸A变为丝氨酸S；同时，CVI988株Meq基因第228位核苷酸由A变为G，导致第77位氨基酸由赖氨酸K变为谷氨酸E。此外，与BJ-1株相比，CVI988株Meq基因在576～578bp之间缺失3个碱基（ACC），并导致第193位脯氨酸P的缺失，该突变发生在一个多脯氨酸重复区域内。结论]MDV-1强弱毒株Meq基因序列存在明显差异，为从其分子水平进行区分及生物学功能的研究奠定了基础。

Clanging and Sequencing Analysis of Meq Gene of Oncogenic and Vaccine Strains of Marek' s Disease Virus Ⅰ

Objective] The aim of the study was to acquire the difference of Meq gene of oncogenic and vaccine strains of Marek' s Disease Virus Ⅰ . Method] According to sequence of Meq gene of Marek's Disease Virus (MDV) in GenBank, a pair of primers was designed for PCR amplification of Meq genes of CVI988/Rispens vaccine strain and Beijing-1 ( BJ-1) velogenic strain of MDV-1. Fragments of Meq were cloned into plasimid pcDNA3.1 ( + ) for analysis of sequences. Result] TheResults showed that the open reading frames of Meq gene of CVI988/Rispens strain and BJ-1 strain werel 200 and 1 197 bp respectively. Compared with Meq genes of MDV-1 reference GA strain, 180 and 177 bp were inserted in Meq genes of BJ-1 and CVI988 strain respectively, and the nucleotide at 211 position changed from G to T,Resulting in the 71 amino acid from serine A to alanine S. In addition, the nucleotide at 228 position changed from A to G in the Meq gene of CVI988 strain, which led to the 77 amino acid glutamic acid from K to E. Three base pairs (ACC ) between 576 bp and 578 bp were deleted in Meq gene of the CVI988 strain ,leading to loss of 193 amino acid proline (P) in internal proline repeat region, not in very virulent BJ-1 strain. Conclusion] Difference of Meq genes of oncogenic and vaccine strains of MDV-1 was obvious. The study laid a foundation for molecular level distinguish of MDV-1 oncogenic and vaccine strains and further study of Meq genes biological function .