Amplification of the initiation region/matrix attachment region (IR/MAR) plasmid.

<p>The IR/MAR (+) plasmid generated double minutes (DMs) (A) or homogeneously staining regions (HSRs) (B) in human COLO 320 cells. In these images, plasmid sequence was detected by FISH (green; indicated by arrows), and chromosomes were counterstained with propidium iodide (PI; red). A previous study revealed the mechanism by which the IR/MAR plasmid generates DMs or HSRs in these cells; these findings are summarized in (C). In the drawing, the plasmid sequence is green, the chromatid is orange, and the centromeres are black circles. In (D)–(F), structures of the three plasmids used in this study are shown. The orientation and position of each PCR primer used for the detection of inverted repeats are depicted as black and red triangles with accompanying numbers. Black and red indicate hybridization to different DNA strands.