PCNA dynamics during the cell cycle. Time-lapse images of HeLa cells stably expressing RNAP2 Ser2ph-mintbody and mCherry-PCNA were acquired. Single confocal sections are shown with the elapsed time (min) and the cell cycle stage. PCNA foci scattered throughout euchromatin in the early S phase became more concentrated with fewer in number in the middle S phase and located at the nuclear periphery and around the nucleolus in the late S phase. Scale bar, 5 µm.