In prostate cancer cells the interaction of C/EBPα with Ku70, Ku80, and poly(ADP-ribose) polymerase-1 increases sensitivity to DNA damage

Abstract

Prostate cancer cell lines were examined for proteins that partnered with the transcription factor C/EBPα by use of a pull-down assay with S-tagged C/EBPα combined with matrix-assisted laser desorption ionization time-of-flight mass spectroscopy analysis. Ku70, Ku80, and poly(ADP-ribose) polymerase-1 (PARP-1) were identified as proteins that associated with C/EBPα. The physical interaction of C/EBPα with these partner proteins was further demonstrated by glutathione S-transferase (GST) pull-downs using purified protein expressed in Escherichia coli. The strongest binding was between C/EBPα and PARP-1. Immunoprecipitation of C/EBPα expressed in prostate cancer cells co-precipitated Ku70, Ku80, and PARP-1. Deletion analysis of C/EBPα indicated that the C terminus of C/EBPα was essential for the interaction of C/EBPα with Ku70, Ku80, and PARP-1. Functional analysis of the interaction between C/EBPα and the Ku proteins as well as PARP-1 showed that cells exhibiting these interactions had increased radiation sensitivity and decreased ability to repair double strand DNA breaks. Deficient DNA repair was dependent on the prostate cancer cell line tested, suggesting a complex process. We conclude that the association of C/EBPα with Ku proteins and PARP-1 raises the likelihood that C/EBPα-expressing prostate cancer cells may be more sensitive to DNA-damaging agents and may be important in the design of new prostate cancer therapies. © 2006 by The American Society for Biochemistry and Molecular Biology, Inc.