Novobiocin treatment reverses radiation-induced alterations in higher-order DNA structure in L5178Y nucleoids.
We have studied the effect of novobiocin treatment on radiation-induced damage and its repair in higher-order DNA structure in two mouse leukemia cell lines differing in their radiosensitivity, L5178Y-R (LY-R) and L5178Y-S (LY-S). We used the fluorescent halo technique to measure alterations in the superhelical density and the topological constraints of DNA in LY-R and LY-S nucleoids. The results for untreated cells show that both cell lines reached maximal DNA unwinding at the same concentration of propidium iodide (PI), whereas LY-S nucleoids were less efficient in their ability to rewind their DNA. The loop size did not differ significantly between the cell lines. Incubation of LY-R and LY-S cells with novobiocin at a concentration which does not influence survival (0.1 mM for 45 min), but inhibits DNA synthesis in LY-R cells (by 28%) to a greater extent than in LY-S cells (by 10%), also causes more DNA unwinding in LY-R nucleoids than in LY-S nucleoids. However, a decreased superhelical density was observed in nucleoids from both cell lines. Novobiocin applied before, and present during, irradiation prevents radiation-induced alterations in DNA supercoiling more efficiently in LY-R than in LY-S cells. The presence of novobiocin during the repair period increased DNA rewinding to levels not significantly different from control values in nucleoids from both cell lines.
Kapiszewska
M
M
Institute of Molecular Biology, Jagiellonian University, Krakow, Poland.
Lange
C S
CS
D000818:Animals; D004249:DNA Damage / Q000187:drug effects*; D004260:DNA Repair / Q000187:drug effects*; D004273:DNA, Neoplasm / Q000187:drug effects / Q000528:radiation effects*; D066298:In Vitro Techniques; D007940:Leukemia L5178 / Q000473:pathology*; D051379:Mice; D009675:Novobiocin / Q000494:pharmacology*; D011836:Radiation Tolerance / Q000502:physiology
D004273:DNA, Neoplasm; D009675:Novobiocin