RESUMO
Earlier studies have determined that the repeat regions of oncogenic serotype 1 MDV (Marek's disease virus) encode a basic leucine zipper protein, Meq, which structurally resembles the Jun/Fos family of transcriptional activators. Meq has been suggested as the MDV-associated oncogene. In this paper, based on the published sequence of Meq gene of GA strain of MDV, a pair of primers were designed and synthesized. Meq gene ORF (Open reading frame) of the four Chinese local MDV isolates, the reference strain J-1 and the vaccine strain 814 were amplified by using polymerase chain reaction(PCR). Then the PCR products were cloned and sequenced respectively. The results of sequence comparison indicated that the sequences of Meq gene in different strains are relatively conserved and homology of the amino acid sequences is 96.5%-99.7%. The proline-rich repeats of Meq gene of four MDV isolates have site mutations, and it is related to MDV's virulence. Two unique site mutations appear in Meq gene of Chinese local MDV isolates, but they aren't present in Meq gene of the published MDV strains from abroad and the early domestic strains. It seems that some regularities exist between such mutations in four Chinese local MDV isolates and the virulence of MDV, but the regularities need further research.