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Nuclear localization of Schizosaccharomyces pombe Mcm2/Cdc19p requires MCM complex assembly

S G Pasion1, S L Forsburg

  • 1The Salk Institute for Biological Studies, Molecular Biology and Virology Laboratory, La Jolla, California 92037, USA.

Molecular Biology of the Cell
|December 10, 1999
PubMed

Insights

Nuclear localization of minichromosome maintenance (MCM) proteins requires their assembly into a complex. This ensures only intact MCM replication factor complexes remain nuclear for proper cell function.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Eukaryotic DNA Replication

Background:

  • Minichromosome maintenance (MCM) proteins MCM2-MCM7 are essential eukaryotic replication factors.
  • These proteins form a heterohexameric complex crucial for DNA replication initiation.
  • In fission yeast, MCM proteins are localized to the nucleus throughout the cell cycle.

Purpose of the Study:

  • To investigate the regulatory mechanisms governing MCM complex assembly and nuclear localization.
  • To identify cis and trans elements responsible for the nuclear localization of the Mcm2p subunit.

Main Methods:

  • Analysis of cis and trans elements for Mcm2p nuclear localization.
  • Mutation studies of individual mcm genes to observe MCM subunit localization.
  • Identification and functional analysis of Mcm2p nuclear localization signals.

Main Results:

  • Mutation of any single mcm gene causes redistribution of wild-type MCM subunits to the cytoplasm.
  • This cytoplasmic redistribution is dependent on an active nuclear export system.
  • Mcm2p nuclear localization signals are identified and shown to be essential for targeting other MCM subunits.

Conclusions:

  • Mcm2p requires association with other MCM proteins for proper nuclear localization, indicating complex assembly is necessary.
  • Nuclear localization of MCM proteins is coupled to their complex assembly.
  • This coupling mechanism ensures that only fully assembled, intact MCM heterohexamers are retained in the nucleus.

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