Postreplication Repair of Ultraviolet Damage to DNA, DNA-Chain Elongation, and Effects of Metabolic Inhibitors in Mouse L Cells

摘要: Alkaline sucrose sedimentation studies of DNA from mouse L cells have demonstrated the following effects several inhibitors nucleic acid and protein synthesis on postreplication repair ultraviolet (UV) damage to their DNA. The newly synthesized by a 2 h [ 3 H]thymidine (dThd) label 254 nm UV irradiation 20 J/m is made in smaller segments number average mol wt (Mn) ∼10×10 6 than control ∼40×10 . presence caffeine at concentration mM during labeling irradiated reduces Mn value 5.8×10 , which nearly comparable to, but somewhat larger expected distance between dimers parental Afterwards, such an interrupted completely repaired present maximum 40×10 consecutive 4 chase unlabeled dThd. inhibitor, either hydroxyurea, 50μM arabinofuranosyl cytosine, excess dThd or 5μg/ml actinomycin D (AMD) 2- 24-h periods after postirradiation prevents various extents, while inhibits it. In unirradiated cells, these agents except also interfere severely with normal elongation nascent 3min pulse label, do not appreciably induce single chain breaks inhibition AMD suggests that de novo close gaps new requires least template-dependent polymerase. contrast, 100μg/ml cycloheximide allows complete gap-filling repair, it simply rates growth for replication. Therefore, similar sensitivity replication towards above indicates preexisting polymerizing system appears be responsible play common role without synthesis, as far early time concerned.