Figure 3.

Association of the transfected plasmid with chromatin. Nuclei isolated from HeLa cells 24 h after transfection with undamaged pZA were mixed with pure pDsRed plasmid and treated with MNase as described in ‘Materials and Methods’ section. (Top) Agarose gel electrophoresis of the fractions obtained by isopycnic centrifugation of the MNase-treated nuclei and of the products of PCR performed with diluted fractions of the same CsCl gradient (numbers indicate the gradient fractions starting from the bottom). M, molecular size marker; nt, no template; p, plasmid DNA. (Bottom) Distribution of the two plasmids (transfected and naked) between the gradient fractions.