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Updated: Oct 3, 2026
Use of Time-Lapse Microscopy and Stage-Specific Nuclear Depletion of Proteins to Study Meiosis in S. cerevisiae
Published on: October 11, 2022
Novel fission yeast Cdc7-Dbf4-like kinase complex required for the initiation and progression of meiotic second
Taro Nakamura1, Michiko Nakamura-Kubo, Tomohiro Nakamura
1Department of Biology, Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka, Japan.
Abstract:
Cdc7, a conserved serine/threonine protein kinase, controls initiation of DNA replication. A regulatory subunit, Dbf4, stimulates the kinase activity of Cdc7 and recruits it to the replication origins. Schizosaccharomyces pombe has a homologous kinase complex, composed of Hsk1 and Dfp1/Him1. Here, we report a novel protein kinase of S. pombe, Spo4, which shares common structural features with the Cdc7 kinases. In spite of the structural similarities, Spo4 is dispensable for mitotic growth and premeiotic DNA replication. Intriguingly, spo4 null mutants are defective in initiation and progression of the second meiotic division. Spindles for meiosis II are often fragmented. Spo4 kinase activity is markedly enhanced when the enzyme is associated with its regulatory subunit, Spo6, a Dbf4-like protein. Expression of Spo4 is specifically induced during meiosis. Spo4 is preferentially present in nuclei, but this nuclear localization does not require Spo6. These results suggest that Spo4 is a Cdc7 kinase whose primary role is in meiosis, not in DNA replication. This is the first report of an organism which has two Cdc7-related kinase complexes with different biological functions.
Insights
Researchers discovered Spo4, a novel protein kinase in fission yeast, which is crucial for the second meiotic division, not DNA replication. This finding reveals two distinct Cdc7-related kinase complexes with unique functions.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Cdc7 kinase and its regulatory subunit Dbf4 are essential for DNA replication initiation.
- Schizosaccharomyces pombe possesses a related complex, Hsk1/Dfp1, involved in DNA replication.
- Understanding novel kinases is key to deciphering complex cellular processes.
Purpose of the Study:
- To identify and characterize novel protein kinases in Schizosaccharomyces pombe.
- To investigate the function of the newly identified kinase, Spo4, and its regulatory subunit, Spo6.
- To determine the role of Spo4 in cell division and DNA replication.
Main Methods:
- Bioinformatic analysis to identify Spo4 based on structural similarity to Cdc7.
- Genetic analysis of spo4 null mutants to assess its role in mitotic and meiotic processes.
- Biochemical assays to study Spo4 kinase activity and its regulation by Spo6.
- Subcellular localization studies of Spo4.
Main Results:
- Spo4, a novel serine/threonine kinase, shares structural similarities with Cdc7 but is dispensable for mitotic growth and premeiotic DNA replication.
- spo4 null mutants exhibit defects in the initiation and progression of the second meiotic division, with fragmented spindles.
- Spo4 kinase activity is enhanced by its regulatory subunit Spo6, a Dbf4-like protein.
- Spo4 expression is induced during meiosis and it localizes to the nucleus, independently of Spo6.
Conclusions:
- Spo4 is a meiosis-specific Cdc7-related kinase, distinct from replication kinases.
- The study identifies two distinct Cdc7-related kinase complexes in S. pombe with different biological roles.
- Spo4 plays a critical role in regulating the second meiotic division.
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