Fig. 1

Generation of DMs from IR/MAR plasmids is dependent on the host cell line. a–g Representative images of IR/MAR plasmids (pSFVdhfr or p∆BN.AR1) after transfection into the indicated cell lines. After blasticidin selection of transfectants for 4–6 weeks, plasmid sequences were detected by FISH in metaphase spreads. The green arrowheads and white arrows indicate chromosomal and extrachromosomal amplification of the plasmid, respectively. Scale bar: 10 μm. h–m Frequencies of chromosomal (white) and extrachromosomal (black) amplification of plasmids in the transfected cell lines were determined by examining more than 30 metaphase chromosome spreads. Shown is a typical result. Quantitatively similar results were obtained from more than 30 (COLO 320DM), more than 5 (MEF, CHO K1), and more than 2 (HeLa, L929 and NIH3T3) independent transfections