The present invention relates to a retroviral vector undergoing promoter conversion comprising a 5'LTR region of the structure U3-R-U5; one or more sequences selected from coding and non-coding sequences; and a 3'LTR region comprising a completely or partially deleted U3 region wherein said deleted U3 region is replaced by a polylinker sequence, followed by the R and U5 region. The retroviral vector undergoes promoter conversion and is useful as a gene transfer vehicle for targeted gene therapy.