Fig. 1. Mitotic fission yeast centromeres are organized in cytologically separable domains. (A) Schematic diagrams of S. pombe centromere structures. Centromere 1 is shown as an example but centromeres 2 and 3 have similar symmetric organization. Top: centromere 1 DNA consists two otr regions containing a region of centromeric outer repeats (dg and dh) flanking a single central core region containing the cnt sequence. Bottom: a putative structure of centromere 1 in sister centromeres at metaphase (based on data in Fig. 1B,C,E and supplemental data at http://jcs.biologists.org/supplemental/). Kinetochores (Kin) are separated and facing opposite spindle poles whereas the otr regions are held together by sister-chromatid cohesion. The central core regions are the bases for Kin structures. (B) Deconvolved IF images of fixed metaphase cells showing two pairs of sister kinetochores. The otr DNA sequences were detected by FISH (green) and are flanked by the kinetochore protein (Ndc80) signal (red). (C) Frames from live imaging movies (see Movies 1 and 2 at http://jcs.biologists.org/supplemental) showing the spindle pole body protein Cut12-CFP (red) along with Ndc80-GFP (green) in one cell (left) and Cut12-GFP (red) along with CFP-Cnp1 (green) in another cell (right). Bottom panel: the graphs show the pixel intensities along the spindle axis in the cells of Cut12 (red) and Cnp1 or Ndc80 as indicated (green). The length of the spindle axis is indicated by large black arrowed lines below each graph and the distance between two adjacent Ndc80 (0.41 µm) or Cnp1 (0.25 µm) signals on the spindle axis are indicated by small black arrowed lines. (D) Top: frames from the movie showing Ndc80-GFP (green) along with CFP-Cnp1 and Cut12-CFP (red) in one cell. The dotted squares represent the pixel position of the Ndc80 signals (see Movies 1 and 2 at http://jcs.biologists.org/supplemental). Bottom: pixel shift control of the Hu1048 strain expressing the same protein in dual colors: Cut12-CFP (green) and Cut12-GFP (red). The perfect colocalization of the two colors of Cut12 (bottom) shows that the pixel differences between Cnp1 and Ndc80 (top) are significant. (A-C) Scale bar: 0.50 µm.

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