HP1 and γH2Av dynamics during mitosis.

Non-synchronized S2 cells were grown under logarithmic conditions, plated in 8-well chambered slides and exposed to irradiation of 25 Gy (5 Gy/min). Immediately after irradiation S2 cells were immunostained and scored for mitotic cells under a confocal microscope based on PH3 staining. (A) Cells were fixed and stained with anti-HP1a antibody (red) and anti-PH3 (green). Different phases of mitosis are shown. (B) Unirradiated cells stained with anti-γH2Av (red) and anti-PH3 (green) showing an absence of IRIFs. (C) γH2Av foci are formed in irradiated mitotic cells. Staining as in (B). An interphase cell (arrow) and a cell in late prophase (arrowhead) are shown in the upper row. The middle and lower rows show cells in anaphase and telophase. Note that the γH2Av foci are less intense at telophase. (D) Graph showing the intensity of chromosomal γH2Av staining at various stages of mitosis relative to PH3, a marker for mitotic chromosomes.