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. 2011 Jun;11(3):218–228. doi: 10.2174/156652311795684740

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© 2011 Bentham Science Publishers Ltd

This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.5/), which permits unrestrictive use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Fig. (1) — Designs of the improved retroviral vectors. (A) Insulator located in U3 of 3’LTR is copied to 5’LTR in target cell. Insulators located in the both ends of vector DNA blocks the cross activation between retroviral DNA and the chromosomal DNA. (B) Due to the duplication of U3-deleted LTR of the SIN vector in target cell, the proviral form does not contain viral enhancer any more, and thus require an internal promoter for the expression of the transgene. Arrows show the transcription start. P, internal promoter; ΔU3, deletion of U3 sequence. (C) Comparison of splicing in conventional and split-intron vectors. Arrows show transcripts from the vector DNA. SD, Splice Donor site; SA, Splice Acceptor site.