STATUS AND TRANSCRIPTIONAL ACTIVITY OF A BOVINE-PAPILLOMAVIRUS-I-BASED EXPRESSION VECTOR IN A RECOMBINANT PRODUCTION CELL-LINE

We have analysed the status and transcriptional activity of the bovine papillomavirus-1 (complete BPV-1 genome)-based expression vector pCES in C127i-cell-line-derived 3T1 cells used for the industrial producti on of recombinant human erythropoietin (rhuEpo). Complete tandem head- to-tail integration of about 600 vector copies at a single site of the cellular genome was observed. Deletions, insertions or rearrangements of pCES-specific sequences or extrachromosomal copies of vector seque nces were not detected. Transcriptional analyses demonstrated that rhu Epo was abundantly expressed, BPV-1 early transcription was detected, as expected from a BPV-1-transformed cell line; however, compared with the mouse metallothionein-1-promoter-driven rhuEpo-specific transcrip tion, it was very weak. Late BPV-1 transcription was also not detected in 3T1 cells under conditions of large-scale rhuEpo production. There fore this expression system proved to be safe and suitable for the pro duction of rhuEpo.