Selective Inhibition of Nuclear DNA Synthesis by 9-β-D-Arabinofuranosyl Adenine in Rat Cells Transformed by Rous Sarcoma Virus

Abstract
The drug, 9-β-D-arabinofuranosyl adenine, selectively inhibits the synthesis of nuclear DNA without affecting extrachromosomal DNA synthesis in rat cells transformed by Rous sarcoma virus (B-mix K-44/6). The inhibition was linear with respect to drug concentration over the range of 37-600 μM. Mitosis and total synthesis of DNA per cell were also depressed. DNA synthesis was determined by measurement of [ 3 H]thymidine incorporation into DNA. Covalently-closed circular DNA was extracted by the Hirt procedure and separated from residual chromosomal DNA by buoyant density gradient ultracentrifugation in CsCl-propidium diiodide. On the basis of buoyant density and sedimentation velocity centrifugation, the covalently-closed circular DNA formed in the presence of the drug was indistinguishable from that formed in its absence.