Non-integrating lentiviral vectors based on the minimal S/MAR sequence retain transgene expression in dividing cells

Safe and efficient gene transfer systems are the basis of gene therapy applications. Non-integrating lentiviral （NIL） vectors are among the most promising candidates for gene transfer tools, because they exhibit high transfer efficiency in both dividing and non-dividing cells and do not present a risk of insertional mutagenesis. However, non-integrating lentiviral vectors cannot in- troduce stable exogenous gene expression to dividing cells, thereby limiting their application. Here, we report the design of a non-integrating lentiviral vector that contains the minimal scaffold/matrix attachment region （S/MAR） sequence （SNIL）, and this SNIL vector is able to retain episomal transgene expression in dividing cells. Using SNIL vectors, we detected the expres- sion of the eGFP gene for 61 days in SNIL-transduced stable CHO cells, either with selection or not. In the NIL group without the S/MAR sequence, however, the transduced cells died under selection for the transient expression of NIL vectors. Further- more, Southern blot assays demonstrated that the SNIL vectors were retained extrachromosomally in the CHO cells. In con- clusion, the minimal S/MAR sequence retained the non-integrating lentiviral vectors in dividing cells, which indicates that SNIL vectors have the potential for use as a gene transfer tool.