Bowman-Birk protease inhibitor activates DNA-dependent protein kinase and reduces formation of radiation-induced dicentric chromosomes

Int J Radiat Biol. 2003 Oct;79(10):801-8. doi: 10.1080/09553000310001610277.

Abstract

Purpose: To test a stimulatory effect of the radioprotector Bowman Birk protease inhibitor (BBI) upon DNA repair processes.

Materials and methods: An effect of BBI upon DNA repair was investigated by quantification of radiation-induced dicentric chromosomes. Sensitivity to ionizing radiation was determined by clonogenic survival assay. Quantification of activity of the DNA-dependent kinase was performed by immunoprecipitation and phosphorylation of a TP53-derived peptide.

Results: The formation of radiation-induced dicentric chromosomes was reduced significantly after pretreatment of cells with BBI. By using a cell line with an inducible expression of a mutated TP53, it was shown that the BBI-mediated reduction of dicentric chromosome formation depended on the presence of wild-type TP53. To get further insights into the molecular mode of action of BBI, activity of the DNA-dependent protein kinase (DNA-PK) was quantified. BBI treatment resulted in a stimulation of basal (DNA-PK) activity. In SCID mouse fibroblasts deficient in DNA-PK activity, BBI failed to reduce the amount of radiation-induced dicentric chromosomes and the radioprotective effect was absent. Likewise, cells expressing mt.TP53 did not show radioprotection by BBI.

Conclusions: It was observed that BBI exerts its radioprotective effect by a reduction of incorrect DNA repair, resulting in a reduced amount of dicentric chromosomes. This effect on the fidelity of DNA repair is TP53 dependent and correlated with induction of DNA-PK activity.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carcinoma, Bronchogenic / genetics
  • Carcinoma, Bronchogenic / metabolism*
  • Cell Line
  • Cell Survival / drug effects
  • Cell Survival / radiation effects
  • Chromosome Aberrations / drug effects*
  • DNA-Activated Protein Kinase
  • DNA-Binding Proteins*
  • Dose-Response Relationship, Radiation
  • Enzyme Activation / drug effects
  • Enzyme Activation / radiation effects
  • Enzyme Activators / pharmacology
  • Fibroblasts / drug effects
  • Fibroblasts / metabolism*
  • Fibroblasts / radiation effects*
  • Lung Neoplasms / metabolism
  • Protein Serine-Threonine Kinases / drug effects
  • Protein Serine-Threonine Kinases / metabolism*
  • Radiation Dosage
  • Radiation-Protective Agents / pharmacology*
  • Severe Combined Immunodeficiency / embryology
  • Severe Combined Immunodeficiency / genetics
  • Severe Combined Immunodeficiency / metabolism
  • Trypsin Inhibitor, Bowman-Birk Soybean / pharmacology*
  • Tumor Cells, Cultured
  • Tumor Suppressor Protein p53 / drug effects
  • Tumor Suppressor Protein p53 / metabolism*

Substances

  • DNA-Binding Proteins
  • Enzyme Activators
  • Radiation-Protective Agents
  • Trypsin Inhibitor, Bowman-Birk Soybean
  • Tumor Suppressor Protein p53
  • DNA-Activated Protein Kinase
  • Protein Serine-Threonine Kinases