Effects of procollagen C-proteinase enhancer protein on the growth of cultured rat fibroblasts revealed by an excisable retroviral vector.

An excisable retroviral vector, TSN-lox, was developed by exploiting Cre-loxP homologous recombination. An integrated TSN-lox provirus could be excised, leaving a solo long terminal repeat at the integration site; inverse PCR, taking advantage of the solo long terminal repeat, was used to characterize cellular flanking sequences. A TSN-lox-transduced Rat2 cell clone, lox-7, was found to harbor the provirus in an intron of the procollagen C-proteinase enhancer protein (PCPE) gene, whose expression was lowered compared with that of the parental Rat2. When the vector provirus in lox-7 cells was excised, PCPE expression was elevated. The level of PCPE expression seemed to affect cell growth properties such as morphology, contact inhibition, and anchorage-independent growth. These results suggested that the excisable retroviral vector may be useful for studying the molecular basis for proviral insertion mutagenesis, and that PCPE may play a significant role in controlling cell growth and differentiation.