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First published online 10 October 2006
doi: 10.1242/jcs.03220
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Research Article |

1 Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
2 Cell Cycle Control Laboratory, Swiss Institute for Experimental Cancer Research (ISREC), 1066 Epalinges, Switzerland
Author for correspondence (e-mail: Dannel.McCollum{at}umassmed.edu)
Accepted 10 August 2006
| Summary |
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Key words: S. pombe, Cdc14, Clp1, Flp1, FEAR network
| Introduction |
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| Results |
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In budding yeast, the FEAR functions to release Cdc14 in early anaphase and this release is required for a number of functions including: M1 exit in meiosis (Buonomo et al., 2003
; Marston et al., 2003
), nuclear positioning (Ross and Cohen-Fix, 2004
), rDNA segregation (D'Amours et al., 2004
; Sullivan et al., 2004
; Torres-Rosell et al., 2004
), MEN activation (Pereira et al., 2002
; Stegmeier et al., 2002
; Tinker-Kulberg and Morgan, 1999
; Visintin et al., 2003
) and passenger protein localization to the spindle (Pereira and Schiebel, 2003
). We have examined whether any of these functions may be conserved in S. pombe. We find that nuclear positioning, passenger protein localization to the spindle all seem normal in the clp1
deleted cells (Trautmann et al., 2001
; Cueille et al., 2001
; Trautmann et al., 2004
) (data not shown). As in budding yeast, Clp1p helps activate the SIN, and sin clp1
double mutants display negative interactions (Trautmann et al., 2001
; Cueille et al., 2001
). However, we did not observe any synthetic interactions between FEAR components and the SIN (data not shown). Therefore these proteins may not contribute to the ability of Clp1p to activate the SIN as is observed in S. cerevisiae.
Because FEAR-dependent release of Cdc14p is essential for progression from meiosis I to meiosis II, we examined whether Clp1p was similarly important for meiotic progression in S. pombe. Meiotic progression in wild-type and clp1
cells was initiated in diploid cells using the pat1-114 mutation. This experiment showed that homozygous clp1
cells progressed through meiosis I and II with almost identical kinetics to that of wild-type cells (Fig. 3A,B). In addition, self matings between h+ and h wild-type or h+ and h clp1
cells showed similar numbers of four-spored asci (Fig. 3C,D). The slight decrease in complete asci in clp1
cells may reflect weakened SIN signaling in the clp1
cells, since SIN signaling is important for spore formation (Krapp et al., 2006
). In both experiments, clp1
cells showed a slight but reproducible increase in the number of asci with two or three nuclei (Fig. 3A,B,D), suggesting that similarly to mitosis, Clp1p has a role in the fidelity of the process. In addition, examination of Clp1p localization in meiosis, showed no difference between wild-type and spo12
cells (data not shown). Together, these and previous results (Samuel et al., 2000
) show that Clp1p and Spo12p do not play an essential role in meiotic progression in fission yeast.
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We next examined whether Clp1p functioned in rDNA and telomere segregation. Nucleolar and telomere segregation was monitored using Nuc1p-GFP to label the nucleolus and a LacO array integrated at the sod2 locus near the telomere in cells expressing LacI-GFP (Ding et al., 2004
). The separation of each signal was analyzed by comparing the amount of time after SPB separation (mitotic entry) before separation of the GFP signals, as well as the distance between SPBs when the nucleolar or telomere GFP signals separate. Interestingly, Nuc1-GFP signals separated at almost the same time post SPB separation. In addition, when the SPBs were separated, the same overall distance was measured in wild-type and clp1
cells (Fig. 4, Table 1). Similarly, telomere separation was not delayed relative to wild-type cells in clp1
cells (Table 2). These results show that Clp1p does not play a significant role in segregation of the nucleolus and telomeres.
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| Discussion |
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| Materials and Methods |
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cells was done as previously described (Krapp et al., 2006| Acknowledgments |
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| Footnotes |
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| References |
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