Evidence for the involvement of substrate cycles in the regulation of deoxyribonucleoside triphosphate pools in 3T6 cells

Journal Article · Mon Aug 05 04:00:00 EDT 1985 · J. Biol. Chem.; (United States)

OSTI ID:6085902

Nicander, B; Reichard, P

Pool sizes of deoxyribonucleoside triphosphates (dNTPs) in cultured cells are tightly regulated by the allosteric control of ribonucleotide reductase. The authors determine the in situ activity of this enzyme from the turnover of the deoxycytidine triphosphate (dCTP) pool in rapidly growing 3T6 mouse fibroblasts, as well as in cells whose DNA replication was inhibited by aphidicolin or amethopterin, by following under steady state conditions the path of isotope from (5-TH)cytidine into nucleotides, DNA, and deoxynucleosides excreted into the medium. In normal cells as much as 28% of the dCDP synthesized was excreted as deoxynucleoside. Inhibition with amethopterin slightly increased ribonucleotide reductase activity, while aphidicolin halved the activity of this enzyme (and thymidylate synthase). This continued synthesis and turnover in the absence of DNA synthesis is in contrast to the earlier found inhibition of dCTP (and dTTP) turnover when hydroxyurea, an inhibitor of ribonucleotide reductase, was used to block DNA synthesis. To explain these results, the authors propose that substrate cycles between deoxyribonucleosides and their monophosphates, involving the activities of kinases and phosphatases, participate in the regulation of pool sizes. Within the cycles, a block of the reductase activates net phosphorylation, while inhibition of DNA polymerase stimulates degradation.

• Research Organization: Karolinska Institutet, Stockholm, Sweden
• OSTI ID: 6085902
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 16; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMIDES
ANIMAL CELLS
ANIMALS
ANTIMETABOLITES
AZINES
BIOCHEMISTRY
CHEMISTRY
CONNECTIVE TISSUE CELLS
CYTIDINE
DNA REPLICATION
DRUGS
ENZYMES
FIBROBLASTS
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
HYDROXYUREA
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LABELLED POOL TECHNIQUES
MAMMALS
METHOTREXATE
MICE
NUCLEIC ACID REPLICATION
NUCLEOSIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDOREDUCTASES
PYRIMIDINES
RIBOSIDES
RODENTS
SOMATIC CELLS
THYMIDINE
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES