Nuclear accumulation of Saccharomyces cerevisiae Mcm3 is dependent on its nuclear localization sequence

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Updated: Oct 31, 2026

Assessment of Submitochondrial Protein Localization in Budding Yeast Saccharomyces cerevisiae
08:55

Assessment of Submitochondrial Protein Localization in Budding Yeast Saccharomyces cerevisiae

Published on: July 19, 2021

M R Young1, K Suzuki, H Yan

  • 1Department of Biological Science, Faculty of Science, Hiroshima University, Kagamiyama, Japan.

Genes to Cells : Devoted to Molecular & Cellular Mechanisms
|January 14, 1998
PubMed
Abstract

Insights

Researchers identified a nuclear localization sequence (NLS) in Mcm3, crucial for its nuclear entry in yeast. This NLS directs Mcm3 into the nucleus, but cell cycle-specific accumulation likely involves nuclear retention mechanisms.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The Mcm2-7 protein family is essential for DNA replication initiation.
  • In Saccharomyces cerevisiae, the nuclear envelope remains intact during mitosis, necessitating regulated nuclear import of large proteins like Mcm.
  • Understanding the mechanisms of nuclear transport for cell cycle-regulated proteins is critical.

Purpose of the Study:

  • To identify and characterize the nuclear localization sequence (NLS) of the Mcm3 protein.
  • To investigate the role of potential phosphorylation sites near the Mcm3 NLS in nuclear import and function.
  • To determine the contribution of the NLS to cell cycle-specific nuclear accumulation of Mcm3.

Main Methods:

  • Identification and mutagenesis of a putative NLS in Mcm3.
  • Functional assays using beta-galactosidase reporter system to assess NLS activity.
  • Analysis of Mcm3 phosphorylation status using two-dimensional gel electrophoresis.
  • Complementation assays and plasmid stability assays to evaluate replication activity.

Main Results:

  • A functional NLS was identified in Mcm3, essential for its nuclear translocation.
  • The identified NLS is sufficient to direct a reporter protein (beta-galactosidase) into the nucleus.
  • Mutations in four adjacent potential phosphorylation sites did not affect Mcm3 nuclear accumulation or cell viability.
  • Substitution of the Mcm3 NLS with the SV40 large T-antigen NLS led to nuclear accumulation but compromised cell growth.

Conclusions:

  • Mcm3 protein is imported into the nucleus via a specific NLS.
  • Cell cycle-specific nuclear accumulation of Mcm3 is likely mediated by nuclear retention or targeting, not solely by NLS-regulated import.
  • The identified NLS plays a key role in Mcm3 nuclear import, but other mechanisms contribute to its regulated nuclear presence.

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