Identification and Characterization of a Xenopus Homolog of Dbf4, a Regulatory Subunit of the Cdc7 Protein Kinase Required for the Initiation of DNA Replication

2003 ◽  
Vol 134 (3) ◽  
pp. 447-457 ◽  
Author(s):  
A. Furukohri
Keyword(s):  
Dna Replication ◽  
Protein Kinase ◽  
Regulatory Subunit ◽  
Initiation Of Dna Replication ◽  
Identification And Characterization

scholarly journals Novel Fission Yeast Cdc7-Dbf4-Like Kinase Complex Required for the Initiation and Progression of Meiotic Second Division

2002 ◽  
Vol 22 (1) ◽  
pp. 309-320 ◽  
Author(s):  
Taro Nakamura ◽  
Michiko Nakamura-Kubo ◽  
Tomohiro Nakamura ◽  
Chikashi Shimoda
Keyword(s):  
Dna Replication ◽  
Protein Kinase ◽  
Kinase Activity ◽  
Structural Features ◽  
Regulatory Subunit ◽  
Primary Role ◽  
Biological Functions ◽  
Cdc7 Kinase ◽  
Initiation Of Dna Replication ◽  
Novel Protein

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.

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