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The NIMA kinase: a mitotic regulator in Aspergillus nidulans and vertebrate cells

K P Lu1, T Hunter

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

Progress in Cell Cycle Research
|January 1, 1995
PubMed

Insights

NIMA, a mitotic protein kinase, is essential for cell cycle progression in eukaryotes. Its activation, alongside CDC2, is crucial for triggering mitosis, suggesting NIMA as a key cell cycle regulator.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • CDC2 regulates entry into mitosis in eukaryotic cells.
  • In Aspergillus nidulans, CDC2 activation alone is insufficient for mitosis; NIMA activation is also required.
  • NIMA and CDC2 share analogous functions and regulatory patterns, both impacting the G2/M transition.

Purpose of the Study:

  • To investigate the role of NIMA in eukaryotic cell cycle regulation.
  • To compare the functions and regulation of NIMA and CDC2.
  • To determine if NIMA represents a novel essential cell cycle regulator.

Main Methods:

  • Comparative analysis of NIMA and CDC2 functions in cell cycle progression.
  • Examination of NIMA activity and regulation during the cell cycle.
  • Studies on the effects of NIMA overexpression and dominant-negative mutants in various cell types (Xenopus oocytes, Aspergillus nidulans, human cells).

Main Results:

  • NIMA activity is tightly regulated throughout the cell cycle.
  • NIMA overexpression induces premature mitosis, while dominant-negative mutants cause G2 arrest, similar to CDC2.
  • NIMA and CDC2 exhibit distinct substrate specificities and regulatory mechanisms (intramolecular for NIMA, intermolecular for CDC2).
  • A NIMA-like pathway is vital for the G2/M transition in vertebrate cells.

Conclusions:

  • NIMA is a critical regulator of the G2/M transition in eukaryotic cells.
  • NIMA's distinct regulatory mechanisms and essential role suggest it is a novel cell cycle regulator.
  • Further research is needed to identify NIMA homologues in other species.

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