title: Processing of abasic DNA clusters in hApeI-silenced primary fibroblasts exposed to low doses of X-irradiation.
abstract: Clustered damage in DNA includes two or more closely spaced oxidized bases, strand breaks or abasic sites that are induced by high- or low-linear-energy-transfer (LET) radiation, and these have been found to be repair-resistant and potentially mutagenic. In the present study we found that abasic clustered damages are also induced in primary human fibroblast cells by low-LET X-rays even at very low doses. In response to the induction of the abasic sites, primary fibroblasts irradiated by low doses of X-rays in the range 10-100 cGy showed dose-dependent up-regulation of the DNA repair enzyme, ApeI. We found that the abasic clusters in primary fibroblasts were more lethal to cells when hApeI enzyme expression was down-regulated by transfecting primary fibroblasts with hApeI siRNA as determined by clonogenic survival assay. Endonuclease activity of hApeI was found to be directly proportional to hApeI gene-silencing efficiency. The DNA repair profile showed that processing of abasic clusters was delayed in hApeI-siRNA-silenced fibroblasts, which challenges the survival of the cells even at very low doses of X-rays. Thus, the present study is the first to attempt to understand the induction of cluster DNA damage at very low doses of low- LET radiation in primary human fibroblasts and their processing by DNA repair enzyme ApeI and their relation with the survival of the cells.
authors: Department of Chemistry, Indian Institute of Technology Patna, Patna 800 013, India. prolay@iitp.ac.in
authors: Prolay
authors: P
authors: Das
authors: Betsy M
authors: BM
authors: Sutherland
mesh_terms: D015153:Blotting, Western; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects*; D004260:DNA Repair / Q000502:physiology*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D004586:Electrophoresis; D005347:Fibroblasts / Q000378:metabolism*; D005453:Fluorescence; D005786:Gene Expression Regulation / Q000528:radiation effects*; D020868:Gene Silencing; D006801:Humans; D009841:Oligonucleotides / Q000235:genetics; D034741:RNA, Small Interfering; D014162:Transfection
chemical_list: D009841:Oligonucleotides; D034741:RNA, Small Interfering; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase