High Resolution Autoradiographic Study of the Kinetics of Development of Rous Sarcoma Virus (Schmidt-Ruppin Strain). V. Estimation of the Time of Synthesis of Virus-Associated DNA

Chick embryo fibroblasts transformed by Rous sarcoma virus were labeled with 3H-thymidine; this percursor was incorporated into the extracellular virus as early as 10 minutes after contact of the cells with the precursor. With electron microscope autoradiography, the DNA was detectable at the level of the budding and mature particles after 10 minutes of pulse labeling and 2 hours of chase. After the virus was purified on sucrose gradients and its nucleic acids were extracted, radioactivity was found in an acid-precipitable material. This material was resistant to NaOH hydrolysis and RNase treatment, but sensitive to DNase digestion.