Eukaryotic Cell doi:10.1128/EC.00119-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
SCHIZOSACCHAROMYCES POMBE NOC3 IS ESSENTIAL FOR RIBOSOME BIOGENESIS AND CELL DIVISION BUT NOT DNA REPLICATION
Christopher R. Houchens*,
Audrey Perreault,
François Bachand,
and
Thomas J. Kelly
Laboratory of Regulation of DNA Replication, Program in Molecular Biology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021; Department of Biochemistry, Université de Sherbrooke, Sherbrooke, Québec, Canada
* To whom correspondence should be addressed. Email:
houchenc{at}mskcc.org.
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Abstract |
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The initiation of eukaryotic DNA replication is preceded by the assembly of pre-replication complexes (pre-RCs) at chromosomal origins of DNA replication. Pre-RC assembly requires the essential DNA replication proteins ORC, Cdc6, and Cdt1 to load the MCM DNA helicase onto chromatin. Saccharomyces cerevisiae ScNoc3, an evolutionarily conserved protein originally implicated in 60S ribosomal subunit trafficking, has been proposed as an essential regulator of DNA replication that plays a direct role during pre-RC formation in budding yeast. We have cloned Spnoc3+, the Schizosaccharomyces pombe homolog of the budding yeast ScNOC3 gene, and functionally characterized the requirement for SpNoc3 protein during ribosome biogenesis, cell cycle progression, and DNA replication in fission yeast. We showed that fission yeast SpNoc3 is a functional homolog of budding yeast ScNoc3 that is essential for cell viability and ribosome biogenesis. We also showed that SpNoc3 is required for the normal completion of cell division in fission yeast. However, in contrast to the proposal that ScNoc3 plays an essential role during DNA replication in budding yeast, we demonstrated that fission yeast cells do enter and complete S phase in the absence of SpNoc3, suggesting that SpNoc3 is not essential for DNA replication in fission yeast.
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