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Azidocytidine is a specific inhibitor of deoxyribonucleotide synthesis in 3T6 cells
Abstract:
2'-Azidocytidine is a specific inhibitor of DNA synthesis in cultured 3T6 mouse fibroblasts. Earlier work (Akerblom, L., Pontis, E., and Reichard, P. (1982) 257, 6776-6782) indicated that the nucleoside, after phosphorylation, acted by inhibiting both ribonucleotide reduction and DNA strand elongation. We now demonstrate that the effect on strand elongation was due to a contamination of azidocytidine with less than 0.3% of arabinosyl cytosine. Pure azidocytidine inhibits specifically ribonucleotide reductase and its effects on DNA synthesis are secondary to this inhibition. The results with azidocytidine concerning the size and turnover of deoxyribonucleoside triphosphate pools parallel those of hydroxyurea and are distinct from those of arabinosyl cytosine. Together with hydroxyurea, azidocytidine is a useful compound in studies aiming at a specific block of the production of deoxynucleoside triphosphates in intact cells. Comparisons of the effects of azidocytidine and arabinosyl cytosine complement earlier studies with hydroxyurea and aphidicolin concerning inter-relations between dNTP synthesis and DNA replication.
Insights
Pure 2'-azidocytidine specifically inhibits ribonucleotide reductase, a key enzyme in DNA synthesis. This finding clarifies its mechanism, distinguishing it from arabinosyl cytosine and making it valuable for studying deoxynucleoside triphosphate production.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- 2'-Azidocytidine was previously thought to inhibit both DNA synthesis and ribonucleotide reduction.
- Earlier studies suggested its mechanism involved inhibiting DNA strand elongation.
Purpose of the Study:
- To clarify the specific mechanism of action of pure 2'-azidocytidine.
- To differentiate its effects from contaminants like arabinosyl cytosine.
- To establish its utility in studying deoxynucleoside triphosphate (dNTP) synthesis.
Main Methods:
- Cell culture (3T6 mouse fibroblasts).
- Biochemical assays to determine enzyme inhibition.
- Analysis of deoxyribonucleoside triphosphate pool size and turnover.
Main Results:
- Pure 2'-azidocytidine specifically inhibits ribonucleotide reductase.
- Observed effects on DNA synthesis are secondary to ribonucleotide reductase inhibition.
- Results regarding dNTP pools parallel hydroxyurea, distinct from arabinosyl cytosine.
Conclusions:
- 2'-Azidocytidine is a specific inhibitor of ribonucleotide reductase.
- It is a valuable tool, alongside hydroxyurea, for blocking dNTP production in cells.
- Its mechanism is distinct from arabinosyl cytosine, aiding research on dNTP synthesis and DNA replication.