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Tobacco retinoblastoma-related protein phosphorylated by a distinct cyclin-dependent kinase complex with Cdc2/cyclin

H Nakagami1, M Sekine, H Murakami

  • 1Graduate School of Biological Sciences, Nara Institute of Science and Technology (NAIST), Japan.

The Plant Journal : for Cell and Molecular Biology
|June 23, 1999
PubMed

Insights

Researchers identified a plant retinoblastoma (Rb)-related gene, NtRb1, in tobacco. This gene interacts with tobacco cyclin D and Cdc2, suggesting a role in plant cell cycle regulation via phosphorylation.

Area of Science:

  • Plant molecular biology
  • Cell cycle regulation
  • Cancer research

Background:

  • The retinoblastoma (Rb) protein is a tumor suppressor crucial for cell cycle and differentiation.
  • Rb's growth-suppressive activity is regulated by cyclin-dependent kinase (CDK) phosphorylation.
  • Rb inactivation is key for G1 to S phase transition.

Purpose of the Study:

  • To clone and characterize a tobacco Rb-related gene (NtRb1).
  • To investigate the interaction of NtRb1 with tobacco cell cycle regulators.
  • To elucidate the role of NtRb1 in plant cell cycle control.

Main Methods:

  • Cloning of Nicotiana tabacum cDNA (NtRb1).
  • Yeast two-hybrid and in vitro binding assays to study protein interactions.
  • Insect cell expression and in vitro phosphorylation assays.
  • Immunoprecipitation using anti-cyclin D antibody.

Main Results:

  • NtRb1 gene expression was detected in all examined tobacco organs.
  • NtRb1 interacts with tobacco cyclin D.
  • Tobacco cyclin D and Cdc2 form a complex capable of phosphorylating NtRb1 in vitro.
  • Cyclin D and Cdc2 are found in a complex in tobacco BY-2 cells.

Conclusions:

  • The plant cdc2 gene modulates the cell cycle.
  • This modulation occurs through phosphorylation of the Rb-related protein (NtRb1).
  • Formation of an active complex between cyclin D and Cdc2 is essential for this process in plants.

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