FIG. 5.

The speckled Mre11 focus pattern is found in nonirradiated S-phase cells. (a) Speckled Mre11 foci are contained in BrdU-positive cells and overlap with BrdU incorporation. Nonirradiated 37Lu human fibroblasts were doubly stained for Mre11 (top panel, red signal) and BrdU incorporation (middle panel, green signal), and the images were merged (bottom panel). Overlap between the two signals appears yellow. The three nuclei that do not stain with BrdU correspond to those containing promyelocytic leukemia protein-associated Mre11 foci (37). (b) Speckled Mre11 foci are contained in PCNA-positive S-phase cells. Cells were doubly labeled for Mre11 (top panel, red signal) and PCNA (middle panel, green signal), and the images were merged (bottom, yellow signal). Overlap between the two signals appears yellow.