INSERTION OF THE HUMAN CYTOMEGALOVIRUS ENHANCER INTO A MYELOPROLIFERATIVE SARCOMA-VIRUS LONG TERMINAL REPEAT CREATES A HIGH-EXPRESSION RETROVIRAL VECTOR

A new retroviral vector is characterized in which the enhancer in the long terminal repeat of myeloproliferative sarcoma virus (MPSV) is com bined with the strong and universally active immediate-early human cyt omegalovirus (hCMV) enhancer. We demonstrate that insertion of the hCM V enhancer increases the amount of vector-specific mRNA in various rod ent cell lines and in human diploid fibroblasts, by at least 3-5-fold. The vector may be particularly useful if high expression of two genes is desired.