A polyomavirus enhancer mutant confers ubiquitous high transcriptional efficiency to the SV40 late promoter.

To identify expression plasmids with high efficiency of transcription and with a broad tissue and cell range, we have constructed a recombinant vector combining the late SV40 promoter and the polyomavirus regulatory region derived from a mutant (PyNB11/1) which displays a very wide host range. We show that these recombinant enhancer-promoters are efficient drivers for heterologous gene transcription and expression in vitro in all mouse and human cells tested. The most active combination we identified contained the mutant enhancer (PyNB11/1) in the late orientation. This construct was able to promote a high efficiency of expression without significant fluctuation between cells of different tissutal origin or different differentiative stage. A possible interpretation of these results is discussed.