Interstitial telomeric DNA sequences of Chinese hamster cells are hypersensitive to nitric oxide damage, and DNA-PKcs has a specific local role in its repair.
The DNA breakage detection-fluorescence in situ hybridization (DBD-FISH) procedure was used to analyze DNA single-strand breaks (SSBs) and alkali-labile sites induced by exposure to the nitric oxide (NO) donors sodium nitroprusside (SNP) and 3-morpholinosydnomine hydrochloride (SIN-1) in the whole genome and in long interstitial telomeric repeat sequence (ITRS) blocks from Chinese hamster cells. The relative density of DNA damage generated in the ITRS by X-rays was similar to that induced in the genome overall, whereas it was 1.7 times higher when the alkylating agent MNNG was assayed. Nevertheless, after SNP or SIN-1 treatment, ITRSs proved to be 2.8 and 2.7 times relatively more damaged, respectively, than the whole genome. When the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) was not active, as in XR-C1 mutant cells, the repair kinetics in the whole genome did not differ from that in the parental cell line with X-ray or SNP exposure. However, whereas the SSBs and alkali-labile sites induced in the ITRS by X-rays exhibited rejoining kinetics similar to that of the parental cell line, the damage induced by SNP was more slowly rejoined. This implies a role for DNA-PKcs in the repair of DNA damage induced by NO, especially in ITRSs. The results demonstrated intragenomic heterogeneity of NO-induced DNA damage and repair; there was a higher density of DNA damage in the ITRS blocks, possibly because of their guanine richness. This suggests that a parallel process may occur in the terminal telomeres, which has implications for premature aging and neoplastic development by chronic NO exposure in vivo.
Mosquera
Alejandro
A
Sección de Genética y Unidad de Investigación, Complejo Hospitalario Universitario Juan Canalejo (CHUJC), As Xubias, Coruña, Spain.
Gosálvez
Jaime
J
Sabatier
Laure
L
Fernández
José Luis
JL
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004249:DNA Damage / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D017404:In Situ Hybridization, Fluorescence; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis
D020030:Nitric Oxide Donors; D008769:Methylnitronitrosoguanidine; C002385:linsidomine; D008981:Molsidomine