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Mouse MCM proteins: complex formation and transportation to the nucleus
H Kimura1, T Ohtomo, M Yamaguchi
1Research Centre for Molecular Genetics, Hokkaido University, Kita, Sapporo, Japan.
Genes to Cells : Devoted to Molecular & Cellular Mechanisms
|November 1, 1996
Summary
Mammalian MCM proteins form a complex essential for DNA replication. This study identifies six mouse MCM proteins forming a 450-600 kDa complex, crucial for cell cycle control.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- The MCM protein family regulates DNA replication initiation in eukaryotes.
- MCM proteins bind chromatin in G1 and detach during S phase, licensing replication.
- Mammalian MCM2 and P1MCM3 localize to the nucleus during interphase.
Purpose of the Study:
- To investigate the composition and properties of the mouse MCM protein complex.
- To determine the role of specific MCM subunits in nuclear localization and chromatin binding.
Main Methods:
- Immunoaffinity chromatography using anti-mCdc21 antibody.
- Purification of associated proteins from mouse cell extracts.
- Glycerol gradient centrifugation to determine complex molecular weight.
- Overexpression in COS cells to assess nuclear localization.
Main Results:
- Six mouse MCM proteins (MCM2, MCM3, Cdc21, CDC46, Mis5, CDC47) co-purified.
- The mouse MCM proteins form a complex of 450-600 kDa.
- mCdc21 dissociates from replicated chromatin during S phase, similar to P1MCM3 and MCM2.
- Only mMCM2 and mP1MCM3 exhibited nuclear localization upon overexpression.
Conclusions:
- In mice, six MCM proteins assemble into a single complex (450-600 kDa).
- This complex is likely involved in regulating DNA replication.
- Nuclear entry of the complex may be mediated by nuclear localization signals in mMCM2 and mP1MCM3 subunits.