| abstract |
A retroviral vector including a multiple cloning site having no greater than about 70 base pairs, and which includes at least four different enzyme restriction sites, wherein at least two of the sites have an average frequency of appearance in eukaryotic genes of less than one in 10,000 base pairs. Such vector may be employed in conjunction with a shuttle cloning vector having complementary cloning sites to accomplish transfers of genes and/or promoters between the shuttle cloning vector and the retroviral vector. Such a system provides for efficient transfer of genes and/or promoters to a retroviral vector without necessitating reconstruction of the entire retroviral vector. Also contemplated within the scope of the present invention is a retroviral vector having a 3' LTR wherein at least the promoter sequence of the 3' LTR is mutated such that the promoter sequence becomes nonfunctional. |