M phase–specific kinetochore proteins in fission yeast Yukinobu Nakaseko, Gohta Goshima, Jun Morishita, Mitsuhiro Yanagida  Current Biology  Volume 11, Issue 8, Pages 537-549 (April 2001) DOI: 10.1016/S0960-9822(01)00155-5

Figure 1 Localization of Dis1-GFP in living cells. GFP images of mitotically dividing cells containing the integrated Dis1-GFP (left panel) and tubulin-GFP (right) taken at 8 s intervals. The arrowhead indicates ellipsoidal aggregates of Dis1-GFP signals; the asterisk indicates dot-like signals; the arrow indicates the completion of fast splitting of the signals. The splitting of the Dis1-GFP signals and the movement of these signals to the poles takes place within 24 s. In images of tubulin-GFP, spindle microtubules are seen. See Movie 1 in the Supplementary material Current Biology 2001 11, 537-549DOI: (10.1016/S0960-9822(01)00155-5)

Figure 2 Double immunostaining of an S. pombe strain containing the integrated Dis1-GFP gene or the dis1+ gene. Cells were cultured in YPD medium at 33°C and fixed by paraformaldehyde. (a) Immunostaining of the cells integrated with the Dis1-GFP. From top to bottom, the panels show stained images of DNA (with DAPI), microtubules (with anti-tubulin antibody TAT1), Dis1-GFP (with anti-GFP), and merged images (red for tubulin and green for Dis1). (b) Wild-type cells were stained with the same procedure as indicated in (a), except that Dis1 was detected by rabbit anti-Dis1 antibodies. The staining patterns observed after either procedure were indistinguishable. Starting with mitotic metaphase cells, each set of panels is presented in two rows from the left. Dis1-GFP signals were located along the spindle in its central region. More than three dots were occasionally observed. The figures in the second row from the right show mitotic anaphase cells. Dis1-GFP signals were seen near the spindle poles and along the mitotic spindle near the poles of late-anaphase and telophase cells. (c) A plot of the frequency of localization of the Dis1 signal on the spindle microtubules versus the length of the microtubules. On the short spindle micro- tubules (about 2 μm), Dis1 locates in the central region (central). In contrast, Dis1 stains both ends of longer spindle microtubules (3–8 μm [pole]). The scale bars represent 5 μm Current Biology 2001 11, 537-549DOI: (10.1016/S0960-9822(01)00155-5)

Figure 3 CHIP analysis of Dis1-Myc. (a) Temperature-sensitive cut9-665 mutant cells bearing an integrated Dis1-Myc gene were cultured in the synthetic EMM2 medium at 26°C before the temperature was shifted to 36°C, and culturing continued for a further 5 hr to arrest cell cycle progression in metaphase. Samples were then taken for the CHIP analysis. Approximately 70%–80% of cells showed hypercondensed metaphase chromosomes after 5 hr at 36°C. Cells carrying the integrated Mis6-Myc gene were used as a control for CHIP analysis. Mis6 is a kinetochore protein. The DNA probes used were cnt1 (central centromere sequence), imr1 (innermost repeat), dg (outer repeat), lys1 (close to cen1), and c1750 (arm sequence). Mis6 is present in the centromere regions throughout the cell cycle, whereas Dis1 associates only with the central centromere region and only during M phase. (b) Double immunostaining of S. pombe cut9 mutant cells integrated with the Dis1-Myc gene. The sample was the same as that taken for CHIP analysis as shown in (a) for mitotic arrest. DNA, Dis1-Myc protein, and microtubules were stained, respectively, with DAPI, anti-Dis1, and anti-tubulin antibody TAT1. (c) Temperature-sensitive cdc25-22 mutant cells bearing an integrated Dis1-Myc gene were cultured in YPD medium at 26°C before the temperaturewas shifted to 36°C, and they were cultured for a further 4 hr to arrest cells in late G2 phase. Cells were released in YPD at 26°C before samples were taken at the indicated times for CHIP analysis. The top and bottom figures show the results of CHIP analysis and the degree of synchrony, respectively. Dis1 associates with the centromeric DNA in an M phase–specific manner. (d) Cold-sensitive nda3 mutant cells bearing an integrated Dis1-Myc gene were cultured in YPD at 33°C before the temperature was shifted to 20°C, and they were cultured for a further 8 hr to arrest cells in prophase. The association of Dis1 with the centromeric DNA was weaker in nda3-311–arrested cells than in cut9-665–arrested cells Current Biology 2001 11, 537-549DOI: (10.1016/S0960-9822(01)00155-5)

Figure 4 Localization of the C-terminal Dis1-YFP fragment and Mis12-CFP protein by double color tagging. Upper panel: A schematic representation of the C-terminal fragment of Dis1 fused with YFP (Cter-YFP). When overproduced from a multicopy plasmid, this fragment was able to complement the cs phenotype of dis1 deletion mutant cells. This expressed fragment lacked the central microtubule binding domain. Lower panel: Comparative localization in the same cells of the Cter-YFP and Mis12-CFP, an authentic centromere protein. The Cter-YFP signal does not locate along microtubules. Instead, it is only found in the nucleus, and it is enriched in the region identical to that of Mis12-CFP. From the left to the right panels, the signal of DNA, Mis12-CFP, Cter-YFP, and merged images (red for Mis12-CFP and green for Cter-YFP) are shown, respectively. The scale bar represents 10 μm Current Biology 2001 11, 537-549DOI: (10.1016/S0960-9822(01)00155-5)

Figure 5 Mtc1, a homolog of Dis1, and its deletion phenotype. (a) Amino acid sequence alignment of Dis1 and Mtc1. A repeat sequence that is found twice within the N to central regions is shown in blue, while microtubule binding domains are in the central to near C-termini (red for Dis1 and green for Mtc1). The microtubule-associating region of Mtc1 lies within the region from amino acids 559–709, while that for Dis1 lies between amino acids 518–646. Coiled-coil regions (amino acids 680–780 for Dis1 and 640-700 for Mtc1) are found near the C termini of both molecules. (b) Gene disruption phenotype of Δmtc1. One-step gene replacement was used to disrupt the mtc1+ gene, and this disruption produced a strain that had a ts growth phenotype. Left panel: gene-disrupted Δmtc1 cells. Right panel: wild-type control. Both were grown in EMM2 medium at 26°C and were then shifted to 36°C for 4 hrs. In Δmtc1 mutant cells, cytoplasmic microtubules were rarely seen, and the anti-tubulin antibody staining pattern was weak, even at 26°C. Cell shape abnormalities were prominent at 36°C. Spindle microtubules can be seen along with aberrant chromosome segregation. Anaphase cells often contained the long, thin spindles, and this finding suggests that Mtc1 might be required for normal anaphase spindles. The scale bar represents 10 μm Current Biology 2001 11, 537-549DOI: (10.1016/S0960-9822(01)00155-5)

Figure 5 Mtc1, a homolog of Dis1, and its deletion phenotype. (a) Amino acid sequence alignment of Dis1 and Mtc1. A repeat sequence that is found twice within the N to central regions is shown in blue, while microtubule binding domains are in the central to near C-termini (red for Dis1 and green for Mtc1). The microtubule-associating region of Mtc1 lies within the region from amino acids 559–709, while that for Dis1 lies between amino acids 518–646. Coiled-coil regions (amino acids 680–780 for Dis1 and 640-700 for Mtc1) are found near the C termini of both molecules. (b) Gene disruption phenotype of Δmtc1. One-step gene replacement was used to disrupt the mtc1+ gene, and this disruption produced a strain that had a ts growth phenotype. Left panel: gene-disrupted Δmtc1 cells. Right panel: wild-type control. Both were grown in EMM2 medium at 26°C and were then shifted to 36°C for 4 hrs. In Δmtc1 mutant cells, cytoplasmic microtubules were rarely seen, and the anti-tubulin antibody staining pattern was weak, even at 26°C. Cell shape abnormalities were prominent at 36°C. Spindle microtubules can be seen along with aberrant chromosome segregation. Anaphase cells often contained the long, thin spindles, and this finding suggests that Mtc1 might be required for normal anaphase spindles. The scale bar represents 10 μm Current Biology 2001 11, 537-549DOI: (10.1016/S0960-9822(01)00155-5)

Figure 6 Association of bovine brain tubulin with truncated fragments of Mtc1. (Left panel) Carboxy-truncated Mtc1 proteins were produced in bacteria, run in SDS polyacrylamide gel electrophoresis, and examined for their ability to interact with bovine tubulin by the far Western methods (Nakaseko et al., 1996). Coomasie brilliant blue staining and immunoblot patterns obtained by anti-tubulin antibodies are shown. (Right panel) Amino-truncated Mtc1 proteins were also examined by the same procedures. These two sets of results clearly showed that the central to C-terminal region was responsible for interacting with microtubules Current Biology 2001 11, 537-549DOI: (10.1016/S0960-9822(01)00155-5)

Figure 7 Comparable localization of Mtc1-GFP, Dis1-GFP, and tubulin-GFP. (a) Living interphase cells revealing Mtc1-GFP signals along cytoplasmic microtubule arrays. The images were taken at 8 s intervals. The dot-like signal (indicated by the arrowhead) moved very quickly along microtubules. See Movie 3a in the Supplementary material. (b) Living mitotic cells again show the dot-like signals, but this time along the spindle. Rapid splitting occurred (indicated by the arrow), but some signals remained in the central spindle region. The regions near the SPBs displayed the Mtc1-GFP signals in prophase and prometaphase cells. Also see Movie 3b in the Supplementary material. (c) Still images of Dis1-GFP, Mtc1-GFP, and tubulin-GFP taken by a CCD camera are shown for comparison, as follows: Dis1-GFP (left), Mtc1-GFP (middle), and tubulin-GFP (right). DNA images stained by Hoechst 33342 are also shown as control. “I” indicates interphase cells; “P” indicates prophase cells; “M” indicates prometa- and metaphase cells; “A” indicates anaphase cells; and “T” indicates telophase cells. The scale bars represent 10 μm Current Biology 2001 11, 537-549DOI: (10.1016/S0960-9822(01)00155-5)

Figure 7 Comparable localization of Mtc1-GFP, Dis1-GFP, and tubulin-GFP. (a) Living interphase cells revealing Mtc1-GFP signals along cytoplasmic microtubule arrays. The images were taken at 8 s intervals. The dot-like signal (indicated by the arrowhead) moved very quickly along microtubules. See Movie 3a in the Supplementary material. (b) Living mitotic cells again show the dot-like signals, but this time along the spindle. Rapid splitting occurred (indicated by the arrow), but some signals remained in the central spindle region. The regions near the SPBs displayed the Mtc1-GFP signals in prophase and prometaphase cells. Also see Movie 3b in the Supplementary material. (c) Still images of Dis1-GFP, Mtc1-GFP, and tubulin-GFP taken by a CCD camera are shown for comparison, as follows: Dis1-GFP (left), Mtc1-GFP (middle), and tubulin-GFP (right). DNA images stained by Hoechst 33342 are also shown as control. “I” indicates interphase cells; “P” indicates prophase cells; “M” indicates prometa- and metaphase cells; “A” indicates anaphase cells; and “T” indicates telophase cells. The scale bars represent 10 μm Current Biology 2001 11, 537-549DOI: (10.1016/S0960-9822(01)00155-5)

Figure 8 A cartoon summarizing the findings of the present study. Dis1 was able to bind to both microtubules and kinetochores. The dynamic behavior of Dis1 during the progression from metaphase to anaphase revealed a very rapid splitting of the fluorescent signal, which finding is consistent with the hypothesis that Dis1 associates with kinetochores during the progression from metaphase to anaphase. Dis1, and presumably also Mtc1, are bound to the central region (cnt) of the essential centromere region that associates with Mis6, CENP-A, and Mis12 Current Biology 2001 11, 537-549DOI: (10.1016/S0960-9822(01)00155-5)