Fig. 4.

pol β synthesis activity on UO and UI nucleosomes. (A) Denaturing gels of UO and UI naked DNA and NuCPs. Shown is the uncut fraction remaining (Top) and increasing size of fragment (Middle and Bottom) after incorporation of nucleotides by pol β into naked DNA or NuCPs. Lanes M are for mock-treated samples (no enzyme present), and lanes P are for samples digested with UDG and APE only. Incubation times are from 1 to 4 h with all three enzymes. (B) Plot of the mean ± 1 SD (three independent experiments) of the average number of nucleotides inserted by pol β into UO DNA (solid line, •), UI DNA (dashed line, □), UO NuCP (solid line, ⋄), and UI NuCP (dashed line, ▵). (C) Denaturing gels of UI naked DNA and NuCPs showing the 5′ end-labeled cleavage product and subsequent addition of radionucleotides to the 3′ terminus. P represents incubation with UDG and APE alone, and the black triangles represent increasing incubation time (30 min to 2 h) with UDG, APE, pol β, and [α-³²P]dCTP.