RT Journal Article T1 The IS2 Element Improves Transcription Efficiency of Integration-Deficient Lentiviral Vector Episomes. A1 Sánchez-Hernández, Sabina A1 Gutierrez-Guerrero, Alejandra A1 Martín-Guerra, Rocío A1 Cortijo-Gutierrez, Marina A1 Tristán-Manzano, María A1 Rodriguez-Perales, Sandra A1 Sanchez, Laura A1 Garcia-Perez, Jose Luis A1 Chato-Astrain, Jesus A1 Fernandez-Valades, Ricardo A1 Carrillo-Galvez, Ana Belén A1 Anderson, Per A1 Montes, Rosa A1 Real, Pedro J A1 Martin, Francisco A1 Benabdellah, Karim K1 HS4 insulator K1 IDLV K1 gene therapy K1 lentiviral vector K1 scaffold or matrix attachment regions AB Integration-defective lentiviral vectors (IDLVs) have become an important alternative tool for gene therapy applications and basic research. Unfortunately, IDLVs show lower transgene expression as compared to their integrating counterparts. In this study, we aimed to improve the expression levels of IDLVs by inserting the IS2 element, which harbors SARs and HS4 sequences, into their LTRs (SE-IS2-IDLVs). Contrary to our expectations, the presence of the IS2 element did not abrogate epigenetic silencing by histone deacetylases. In addition, the IS2 element reduced episome levels in IDLV-transduced cells. Interestingly, despite these negative effects, SE-IS2-IDLVs outperformed SE-IDLVs in terms of percentage and expression levels of the transgene in several cell lines, including neurons, neuronal progenitor cells, and induced pluripotent stem cells. We estimated that the IS2 element enhances the transcriptional activity of IDLV LTR circles 6- to 7-fold. The final effect the IS2 element in IDLVs will greatly depend on the target cell and the balance between the negative versus the positive effects of the IS2 element in each cell type. The better performance of SE-IS2-IDLVs was not due to improved stability or differences in the proportions of 1-LTR versus 2-LTR circles but probably to a re-positioning of IS2-episomes into transcriptionally active regions. SN 2162-2531 YR 2018 FD 2018-08-18 LK http://hdl.handle.net/10668/12961 UL http://hdl.handle.net/10668/12961 LA en DS RISalud RD Feb 18, 2025