Abstract: In order to research the regulation of MAR⁃mediated retroviral vector on transgene expression，the report geneCATwas firstly inserted into retroviral vector，the cloned β⁃globin MAR DNA fragment was then inserted respectively into 5'or 3'ends of the vectors，resulting the retroviral vectors series contained MAR in different sites. The recombinated vectors were transfected into PA317 cells. The positive cells were screened by G418，Bel⁃7404 was screened by G418 after transfected by virus from PA317, and theCATgene expression was analyzed by ELISA. The results showed that，compared to the control，the MAR inserted at the 3' end of the vector could enhance theCATgene expression significantly by 11 times（P<0.05），while theCATgene expression was not enhanced when the MAR was inserted at the 5' end of the vector（P>0.05）. These results indicated that MAR could increase the expression level of reporter gene and the regulation of MAR on transgene expression is relied on the inserted site.

Key words: matrix attachment region, gene silencing, gene therapy, position effect