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Updated: Aug 1, 2026
Spatiotemporal Analysis of Cytokinetic Events in Fission Yeast
Published on: February 20, 2017
Fission yeast Clp1p phosphatase regulates G2/M transition and coordination of cytokinesis with cell cycle progression
S Trautmann1, B A Wolfe, P Jorgensen
1Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
Background:
In Saccharomyces cerevisiae the mitotic-exit network (MEN) functions in anaphase to promote the release of the Cdc14p phosphatase from the nucleolus. This release causes mitotic exit via inactivation of the cyclin-dependent kinase (Cdk). Cdc14p-like proteins are highly conserved; however, it is unclear if these proteins regulate mitotic exit as in S. cerevisiae. In Schizosaccharomyces pombe a signaling pathway homologous to the MEN and termed the septation initiation network (SIN) is required not for mitotic exit, but for initiation of cytokinesis and for a cytokinesis checkpoint that inhibits further cell cycle progression until cytokinesis is complete.
Results:
We have identified the S. pombe Cdc14p homolog, Clp1p, and show that it is not required for mitotic exit but rather functions together with the SIN in coordinating cytokinesis with the nuclear-division cycle. As cells enter mitosis, Clp1p relocalizes from the nucleolus to the spindle and site of cell division. Clp1p exit from the nucleolus does not depend on the SIN, but the SIN is required for keeping Clp1p out of the nucleolus until completion of cytokinesis. Clp1p, in turn, may promote the activation of the SIN by antagonizing Cdk activity until cytokinesis is complete and thus ensuring that cytokinesis is completed prior to the initiation of the next cell cycle. In addition to its roles in anaphase, Clp1p regulates the G2/M transition since cells deleted for clp1 enter mitosis precociously and cells overexpressing Clp1p delay mitotic entry. Unlike Cdc14p, Clp1p appears to antagonize Cdk activity by preventing dephosphorylation of Cdc2p on tyrosine.
Conclusions:
S. pombe Clp1p affects cell cycle progression in a markedly different manner than its S. cerevisiae homolog, Cdc14p. This finding raises the possibility that related phosphatases in animal cells will prove to have important roles in coordinating the onset of cytokinesis with the events of mitosis.
Insights
In fission yeast, Clp1p, a homolog of Saccharomyces cerevisiae Cdc14p, coordinates cell division by regulating cytokinesis and the cell cycle. Unlike its budding yeast counterpart, Clp1p does not control mitotic exit but ensures proper timing of cell division.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- The mitotic-exit network (MEN) in Saccharomyces cerevisiae regulates mitotic exit by releasing Cdc14p phosphatase.
- A homologous pathway, the septation initiation network (SIN), in Schizosaccharomyces pombe is crucial for cytokinesis initiation and checkpoint control.
- The precise role of Cdc14p-like proteins in regulating cell division, particularly cytokinesis, remains to be fully elucidated in diverse organisms.
Purpose of the Study:
- To identify and characterize the Schizosaccharomyces pombe homolog of Cdc14p, named Clp1p.
- To investigate the function of Clp1p in relation to the septation initiation network (SIN) and its role in cell cycle progression and cytokinesis.
- To compare the function of Clp1p in S. pombe with Cdc14p in S. cerevisiae.
Main Methods:
- Identification of the S. pombe Cdc14p homolog, Clp1p.
- Analysis of Clp1p localization during the cell cycle using microscopy.
- Genetic analysis involving deletion and overexpression of the clp1 gene.
- Investigation of the interplay between Clp1p and the SIN pathway.
- Biochemical assays to determine Clp1p's effect on Cdk activity.
Main Results:
- Clp1p is essential for coordinating cytokinesis with the nuclear-division cycle, functioning with the SIN pathway.
- Clp1p relocalizes from the nucleolus to the spindle and division site during mitosis.
- While Clp1p's exit from the nucleolus is SIN-independent, the SIN is required to retain Clp1p in the nucleolus until cytokinesis completion.
- Clp1p antagonizes cyclin-dependent kinase (Cdk) activity, potentially by preventing Cdc2p dephosphorylation, ensuring cytokinesis precedes the next cell cycle.
- Clp1p influences the G2/M transition; clp1 deletion leads to precocious mitosis, while overexpression delays it.
Conclusions:
- Schizosaccharomyces pombe Clp1p plays a distinct role in cell cycle progression compared to its S. cerevisiae homolog, Cdc14p.
- Clp1p is critical for coordinating cytokinesis with mitosis, acting through the SIN pathway.
- The findings suggest that related phosphatases in animal cells may coordinate cytokinesis with mitotic events.
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