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Identification of G1 kinase activity for cdk6, a novel cyclin D partner

M Meyerson1, E Harlow

  • 1Massachusetts General Hospital Cancer Center, Charlestown 02129.

Molecular and Cellular Biology
|March 1, 1994
PubMed

Insights

The human PLSTIRE gene product, cdk6 (cyclin-dependent kinase 6), is a novel cell cycle regulator. It links growth factor signals to cell cycle progression by phosphorylating pRB during the G1 phase.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Vertebrate cdc2-related kinases are implicated in cell cycle regulation.
  • The precise roles of specific cyclin-dependent kinases (CDKs) in cell cycle control require further elucidation.

Purpose of the Study:

  • To identify and characterize novel cyclin-dependent kinases involved in cell cycle regulation.
  • To investigate the function and regulation of the human PLSTIRE gene product, identified as cdk6.

Main Methods:

  • Western blotting to detect protein associations.
  • Co-expression in Sf9 insect cells to assess kinase activation.
  • In vitro kinase assays using human cell extracts.
  • Analysis of T cell activation and cell cycle progression.

Main Results:

  • The human PLSTIRE gene product was identified as a novel cyclin-dependent kinase, cdk6.
  • Cdk6 associates with cyclins D1, D2, and D3 in human cells and is activated by D-type cyclins.
  • Endogenous cdk6 from human cell extracts is an active kinase that phosphorylates pRB (retinoblastoma tumor suppressor gene product).
  • Cdk6 activation occurs in mid-G1 phase of phytohemagglutinin-stimulated T cells, preceding cdk2 activation.

Conclusions:

  • Cdk6 is a novel cyclin-dependent kinase that plays a critical role in cell cycle regulation.
  • Cdk6 links growth factor stimulation to the initiation of cell cycle progression by phosphorylating pRB.
  • The timing of cdk6 activation suggests its importance in the early G1 phase of the cell cycle, potentially coordinating with cdk4 in this process.

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