title: Enhancement of frequencies of restriction endonuclease-induced chromatid breaks by arabinoside adenine in normal human and ataxia telangiectasia cells.
abstract: The effect of ara A (9-beta-D-arabino furanosyladenine) a potent inhibitor of DNA synthesis on the frequencies of chromatid breaks induced by restriction endonucleases (RE) has been investigated in normal human and ataxia telangiectasia (AT) lymphoblastoid cells. PvuII, PstI and BamHI which cause blunt-ended, 3'-overhang and 5'-overhang cohesive-ended DNA double-strand breaks (dsb) respectively, were introduced into two AT cell lines (AT-KM and AT-PA) and a normal human (N-SW) cell line by the use of streptolysin-O poration. Controls were exposed to gamma-irradiation and similarly treated with or without ara A. Both AT cell lines were found to exhibit higher frequencies of chromatid breaks when treated with RE alone as compared with the normal cell line. The pattern of chromatid response to the three RE was shown to be similar in all three cell lines i.e. PvuII was most clastogenic while PstI and BamHI were both less effective at inducing chromosomal aberrations. Incubation of cells with ara A resulted in an increase in frequencies of chromatid breaks in PvuII and PstI treated cells but no increase was observed in BamHI treated cells. Normal cells showed most response to ara A following treatment with PvuII and PstI (enhancement ratios 4.63 and 3.75 respectively) while AT cells were affected by ara A to a lesser extent indicating a reduced expression of damage by ara A in these lines. Since ara A is a potent inhibitor of DNA synthesis, it was concluded from the elevated frequency of chromosomal aberrations in the presence of ara A that rejoining of RE-induced dsb in genomic DNA of human cells involves nucleotide insertion at dsb termini prior to ligation.
authors.affiliation: Biomedical and Biotechnogical Research Program, Lawrence Livermore National Laboratory, CA 94551, USA.
authors.forename: N
authors.initials: N
authors.lastname: Liu
authors.forename: P E
authors.initials: PE
authors.lastname: Bryant
mesh_terms: D000963:Antimetabolites / Q000494:pharmacology*; D001260:Ataxia Telangiectasia / Q000473:pathology*; D002460:Cell Line; D002461:Cell Line, Transformed; D002842:Chromatids / Q000187:drug effects*; D004247:DNA / Q000187:drug effects / Q000378:metabolism; D015245:Deoxyribonuclease BamHI / Q000494:pharmacology; D015252:Deoxyribonucleases, Type II Site-Specific / Q000494:pharmacology*; D004357:Drug Synergism; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects* / Q000648:ultrastructure*; D014740:Vidarabine / Q000494:pharmacology*
chemical_list: D000963:Antimetabolites; D004247:DNA; D015245:Deoxyribonuclease BamHI; C025630:CAGCTG-specific type II deoxyribonucleases; C024388:CTGCAG-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific; D014740:Vidarabine