Effects of different thymidine concentrations on DNA replication in pea-root cells synchronized by a protracted 5-fluorodeoxyuridine treatment
Single-cell and DNA fiber autoradiography, cytophotometry and velocity sedimentation in alkaline sucrose gradients were used to analyse DNA replication and nascent replicon maturation in 5-fluorodeoxyuridine (FUdR)-synchronized cells of Pisum sativum. The replicon size was not significantly changed by the protracted FUdR treatment. When the synchronized cells were released from the inhibitor, labeled with (/sup 3/H)TdR for 30 min, and chased in medium containing 1 x 10/sup -6/ M or lower concentrations of cold thymidine, DNA replication stopped after approx. 25% of the genome had replicated, and the nascent strands failed to grow above 9-12 x 10/sup 6/ D single-stranded (ss) DNA. When the cells were chased in medium with 1 x 10/sup -5/ M cold thymidine, the DNA content of the labeled cells steadily increased with time and the size of the nascent molecules grew continuously until replicon size was achieved; then they were accumulated at replicon size until the cells arrived in late S or G2. When the FUdR-synchronized cells were chased in medium containing 1 x 10/sup -4/ M cold thymidine, the size of the nascent strands increased continuously with time, indicating that some neighboring nascent replicons were joined as soon as they completed their replication. These observations led us to postulate that in FUdR-synchronized cells the rates of chain elongation, cell progression through the S phase and nascent replicon maturation are controlled by thymidine availability.
- Research Organization:
- Brookhaven National Lab., Upton, NY
- OSTI ID:
- 5932340
- Journal Information:
- Exp. Cell Res.; (United States), Journal Name: Exp. Cell Res.; (United States) Journal Issue: 2 Vol. 150:2; ISSN ECREA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ANTI-INFECTIVE AGENTS
ANTIMETABOLITES
ANTIMICROBIAL AGENTS
AZINES
BIOLOGICAL EFFECTS
DNA REPLICATION
DRUGS
FLUOROURACILS
FUDR
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEGUMINOSAE
NUCLEIC ACID REPLICATION
NUCLEOSIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PISUM
PLANTS
PYRIMIDINES
RADIOSENSITIZERS
RIBOSIDES
ROOTS
THYMIDINE
TRACER TECHNIQUES
TRITIUM COMPOUNDS
URACILS