INHIBITION OF RIBONUCLEIC ACID SYNTHESIS IN NEWCASTLE DISEASE VIRUS-INFECTED CELLS BY PUROMYCIN AND 6-AZAURIDINE

Abstract

Puromycin and 6-azauridine were used to inhibit protein and ribonucleic acid (RNA) synthesis during Newcastle disease virus replication. Viral RNA, measured by the incorporation of uridine-2-C14, increased rapidly 6 to 7 hr after infection and reached a peak at 12 hr. Viral RNA synthesis was inhibited by puromycin added at the time of infection or at any time up to 4 hr after infection, but not therafter. 6-Azauridine (3 mg/ml) inhibited over 90% of the viral RNA synthesis and inhibited protein synthesis to a small extent. Infected cells synthesized more viral RNA than did untreated controls when exposed to azauridine alone for 5 hr, followed by puromycin alone for 9 hr. It was concluded that immediately after virus infection, virus-specific proteins, which are necessary for viral RNA synthesis, were synthesized. Virus-specific protein synthesis may occur even when viral RNA synthesis is greatly inhibited. After virus-specific protein synthesis has taken place, viral RNA synthesis may take place when protein synthesis is almost totally inhibited.