SEQUENTIAL ALTERATIONS IN THE NUCLEAR CHROMATIN REGION DURING MITOSIS OF THE FISSION YEAST SCHIZOSACCHAROMYCES-POMBE - VIDEO FLUORESCENCE MICROSCOPY OF SYNCHRONOUSLY GROWING WILD-TYPE AND COLD-SENSITIVE CDC MUTANTS BY USING A DNA-BINDING FLUORESCENT-PROBE

Abstract

Video-connected fluorescence microscopy was introduced to study the yeast nuclear chromatin region. It was defined as the nuclear area where a DNA-binding fluorescent probe 4'',6-diamidino-2-phenylindole specifically bound and fluoresced. The 3-dimensional feature of the mitotic chromatin region was deduced by analyzing the successive video images of a cell viewed at different angles. By investigating a synchronous culture of the wild-type fission yeast S. pombe, sequential structural alterations in the chromatin region during mitosis were found. Compaction of the chromatin region from the regular hemispherical form, the formation of a U-shaped intermediate and the rapid segregation into 2 daughter hemispherical forms occurred. Six cs cdc mutants, apparently blocked in mitosis, were observed by fluorescence microscopy. Under the restrictive conditions their chromatin regions exhibited either hemispherical, compact, disk-like, U-shaped or partially segregated chromatin regions. Two mutants showed anomalous nuclear locations. The results of the temperature shift-up experiments of the highly reversible KM52 and KM108 strains supported the above scheme of sequential alterations of the chromatin region.