Identification and characterization of a small inhibitory peptide that can target DNA-PKcs autophosphorylation and increase tumor radiosensitivity.

Abstract

PURPOSE:

The DNA protein kinase catalytic subunit (DNA-PKcs) is one of the critical elements involved in the DNA damage repair process. Inhibition of DNA-PKcs results in hypersensitivity to ionizing radiation (IR); therefore, this approach has been explored to develop molecular targeted radiosensitizers. Here, we aimed to develop small inhibitory peptides that could specifically target DNA-PKcs autophosphorylation, a critical step for the enzymatic activation of the kinase in response to IR.

METHODS AND MATERIALS:

We generated several small fusion peptides consisting of 2 functional domains, 1 an internalization domain and the other a DNA-PKcs autophosphorylation inhibitory domain. We characterized the internalization, toxicity, and radiosensitization activities of the fusion peptides. Furthermore, we studied the mechanisms of the inhibitory peptides on DNA-PKcs autophosphorylation and DNA repair.

RESULTS:

We found that among several peptides, the biotin-labeled peptide 3 (BTW3) peptide, which targets DNA-PKcs threonine 2647 autophosphorylation, can abrogate IR-induced DNA-PKcs activation and cause prolonged γ-H2AX focus formation. We demonstrated that BTW3 exposure led to hypersensitivity to IR in DNA-PKcs-proficient cells but not in DNA-PKcs-deficient cells.

CONCLUSIONS:

The small inhibitory peptide BTW3 can specifically target DNA-PKcs autophosphorylation and enhance radiosensitivity; therefore, it can be further developed as a novel class of radiosensitizer.

• Authors: Xiaonan Sun, Chunying Yang, Hai Liu, Qi Wang, Shi-Xiu Wu, Xia Li, Tian Xie, Kathryn L Brinkman, Bin S Teh, E Brian Butler, Bo Xu, Shu Zheng
• Journal: International journal of radiation oncology, biology, physics (Int J Radiat Oncol Biol Phys) Vol. 84 Issue 5 Pg. 1212-9 (Dec 01 2012) ISSN: 1879-355X [Electronic] United States
• PMID: 22592045 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
• Copyright: Copyright © 2012 Elsevier Inc. All rights reserved.

Chemical References

• BTW3 peptide
• H2AX protein, human
• Histones
• Peptides
• Protein Kinase Inhibitors
• Recombinant Fusion Proteins
• Threonine
• Biotin
• DNA-Activated Protein Kinase

Topics

• Amino Acid Sequence
• Biotin (analogs & derivatives, chemical synthesis, pharmacology)
• DNA End-Joining Repair
• DNA-Activated Protein Kinase (antagonists & inhibitors, metabolism)
• Drug Screening Assays, Antitumor (methods)
• Enzyme Activation (drug effects)
• Histones (biosynthesis)
• Humans
• Molecular Targeted Therapy (methods)
• Peptides (chemical synthesis, pharmacology)
• Phosphorylation (drug effects)
• Protein Kinase Inhibitors (chemistry, pharmacology)
• Radiation Tolerance (drug effects)
• Recombinant Fusion Proteins (chemistry, pharmacology)
• Threonine (antagonists & inhibitors)