FIG. 3.

Nuclear shrinkage and chromosomal aberration of the fbh1 mutant following UV irradiation. (A) Cells of wild-type (MP111), fbh1Δ (MPF3), rhp51Δ (B54), and fbh1Δ rhp51Δ (MPF25) strains were UV irradiated (200 J/m²), cultured for 6 h at 30°C, fixed with glutaraldehyde (2.5%), stained with DAPI (1 μg/ml), and then photographed using a fluorescence microscope. Representative cells with shrunken or normal nuclei are shown. The scale bar indicates 10 μm. (B) fbh1Δ (MPF3) cells or wild-type (MP111) cells UV irradiated and fixed as described above (A) were stained with DAPI (1 μg/ml) and ethidium bromide (10 μg/ml) and then photographed using a fluorescence microscope. The chromosomal region stained with DAPI and nucleolar region (less bright) stained with ethidium bromide are shown by arrows and arrowheads, respectively. The scale bar indicates 10 μm. (C) Wild-type (MPF111), fbh1Δ (MPF3), rhp51Δ (B54), and fbh1Δ rhp51Δ (MPF25) cells were UV irradiated (200 J/m²). Chromosomes of cells before (−) and 2, 4, or 6 h after UV irradiation were analyzed by pulsed-field gel electrophoresis. Chromosomes from 10⁸ cells were loaded onto each lane. The three chromosomes of S. pombe are indicated by I, II, and III, respectively. (D and E) Wild-type (MP111) or fbh1Δ (MPF3) cells were UV irradiated (200 J/m²) and then cultivated in YES medium at 30°C. Cell numbers were scored at the indicated time after irradiation (D). Cells were fixed in 70% ethanol and processed for fluorescence-activated cell sorter analysis (E) as described previously (45).