Characterization of a foot-and-mouth disease mutant temperature-sensitive for viral RNA synthesis

Abstract

A temperature-sensitive (ts) mutant of foot-and-mouth disease virus (FMDV) did not produce RNA polymerase activity nor synthesize viral RNA when incubated in cells solely at the nonpermissive temperature (38.5 degrees C). Infected cells initially incubated at 38.5 degrees C and then shifted down to 33 degrees C synthesized increased amounts of viral RNA at earlier times compared to infected cells kept at 33 degrees C throughout, indicating that RNA polymerase precursors were synthesized at 38.5 degrees C. In cells shifted up to 38.5 degrees C from 33 degrees C, the total amount of viral RNA synthesized after infection increased sharply for about 15 minutes and then rapidly increased over the next 2 hours. RNA polymerase activity presented a similar pattern in its initial twofold increase and subsequent rapid decrease. Pulse labeling experiments showed that mutant viral RNA synthesis continued at a diminishing rate for 2 hours in cells shifted up to 38.5 degrees C. The data from temperature after shift-up was degraded. The FMDV ts mutant is apparently additionally defective in being unable to protect viral RNA synthesized after shift-up to 38.5 degrees C.

Partial Characterization of Temperature-Sensitive Mutants of Foot-and-Mouth Disease Virus, Oi Caseros Strain

“…A similar degradative process was demon strated for some ts mutants by Polatnick and Richmond [6] and by Manor and Goldblum [14], but the first authors did not detect degradation with wt FMDV, strain A-24. A regulatory mechanism appears to operate at the NPT, inducing the degradation of only the RNA synthesized in excess, for the same amount of infectious virus was obtained at both tempera tures.…”

“…ts mutations of foot-andmouth disease virus (FMDV) have been used in genetic [3], physiologic [4][5][6], and patho genic [7] studies. Recently, internal interfer ence has also been described [8].…”