Epstein-Barr virus-based vectors that replicate in rodent cells

Vectors based on Epstein-Barr virus (EBV) have been useful for cloning and gene expression studies in primate cells. However, these vectors do not replicate in rodent cells. We demonstrate here that the addition of large fragments of mammalian DNA to vectors containing the EBNA-1 gene (encoding the Epstein-Barr nuclear antigen-1) and the family of repeats from EBV generates autonomously replicating vectors which are stably maintained as extrachromosomal plasmids in hamster cells. By using a density-shift assay in Cs 2SO 4 density gradients, we demonstrate that the plasmids replicate once per cell cycle at high efficiency. These plasmids represent, for rodent cells, the only available class of stable, autonomous vectors replicating once per cell cycle. It is likely that this type of EBV-based autonomous replication system can also be extended to other organisms for which stable, extrachromosomal plasmid systems are not available.