TRANSCRIPTIONAL ACTIVITY IN 3T3, F9, AND PCC4 EMBRYONAL CARCINOMA-CELLS - A SYSTEMATIC DELETION AND LINKER-SCANNING STUDY OF THE POLYOMAVIRUS ENHANCER

The polyomavirus (PyV) genome is not expressed in undifferentiated emb ryonal carcinoma (EC) cells such as PCC4 or F9 EC cells. All the viral mutants that have been selected for their expression in these cells h arbor mutations or rearrangements within a region which is Important f or early and late transcription (as transcriptional enhancer) as well as for viral DNA replication. We have studied the role of the differen t parts of this enhancer an the transcription driven by early PyV prom oter. Two series of constructions containing progressive deletions sta rting from the ends of the region and one series containing linker-sca nning mutations were tested in a luciferase assay in three cell lines: 3T3, F9, or PCC4 The results revealed that some regions that have not yet been shown to bind transcription factors are nevertheless importa nt for transcriptional activity. Two subregions between nucleotides 51 79 and 5187 and between-5220 and 5227 Were found to be inhibitory for the activity of the enhancer in EC cells. The PEA1/AP1 binding site wa s also unexpectedly shown to be important in F9 EC cells. (C) 1994 Aca demic Press, Inc.