Postreplication repair of ultraviolet damage to DNA, DNA-chain elongation, and effects of metabolic inhibitors in mouse L cells

Journal Article · Thu May 01 04:00:00 EDT 1975 · Biophys. J., v. 15, no. 5, pp. 403-415

DOI:https://doi.org/10.1016/S0006-3495(75)85826-7· OSTI ID:4151491

Fujiwara, Y

Alkaline sucrose sedimentation studies of DNA from mouse L cells have demonstrated the following effects of several inhibitors of nucleic acid and protein synthesis on postreplication repair of ultraviolet (uv) damage to their DNA. The DNA newly synthesized by a 2 h[$sup 3$H]thymidine (dThd) label following 254 nm uv irradiation of 20 J/m$sup 2$ is made in smaller segments of the number average mol wt (Mn) of approximately 10 x 10$sup 6$ than the control of approximately 40 x 10$sup 6$. The presence of caffeine at a concentration of 2 mM during the labeling of the irradiated cells reduces the Mn value to 5.8 x 10$sup 6$, which is nearly comparable to, but somewhat larger than the expected distance between dimers in parental DNA. Afterwards, such an interrupted DNA made in the irradiated cells is completely repaired to the present maximum Mn value of 40 x 10$sup 6$ in the consecutive 4 h chase in unlabeled dThd. The presence of the nucleic acid inhibitor, either 2 mM hydroxyurea, 50 $mu$M arabinofuranosyl cytosine, 2 mM excess dThd or 5 $mu$g/ml of actinomycin D (AMD) during 2- to 24-h chase periods after a 2 h postirradiation label prevents the repair to various extents, while 2 mM caffeine completely inhibits it. In the unirradiated cells, these agents except excess dThd and caffeine also interfere severely with normal elongation of nascent DNA made by a 3 min pulse label, but do not appreciably induce single chain breaks of either newly synthesized or parental DNA. The inhibition of the repair by AMD suggests that de novo elongation of DNA to close the gaps in new DNA made in the irradiated cells requires at least a template-dependent DNA polymerase. (auth)

• Research Organization: Kobe Univ., Japan
• Sponsoring Organization: USDOE
• NSA Number: NSA-33-007425
• OSTI ID: 4151491
• Journal Information: Biophys. J., v. 15, no. 5, pp. 403-415, Journal Name: Biophys. J., v. 15, no. 5, pp. 403-415; ISSN BIOJA
• Country of Publication: United States
• Language: English

Related Subjects

*ACTINOMYCIN-- RADIOSENSITIVITY EFFECTS
*CAFFEINE-- RADIOSENSITIVITY EFFECTS
*CYCLOHEXIMIDE-- RADIOSENSITIVITY EFFECTS
*CYTOSINE-- RADIOSENSITIVITY EFFECTS
*DNA REPLICATION-- BIOLOGICAL RADIATION EFFECTS
*DNA-- BIOLOGICAL REPAIR
*UREA-- RADIOSENSITIVITY EFFECTS
560114* --Biomedical Sciences
Applied Studies--Radiation Effects--Radiation Effects on Biochemicals--In Animals
IRRADIATION
L CELLS
N48140* --Life Sciences--Radiation Effects on Biochemicals-- In Animals
N48210 --Life Sciences--Radiation Effects on Cells--External Source
ULTRAVIOLET RADIATION