HEp-2 cells were pulse-labeled at different times after
infection with herpes simplex virus, and nuclear
ribonucleic acid (
RNA) and cytoplasmic
RNA were examined. The data showed the following: (i) Analysis by acrylamide gel electrophoresis of cytoplasmic
RNA of cells infected at high multiplicities [80 to 200 plaque-forming units (PFU)/cell] revealed that
ribosomal RNA (rRNA) synthesis falls to less than 10% of control (uninfected cell) values by 5 hr after
infection. The synthesis of 4S
RNA also declined but not as rapidly, and at its lowest level it was still 20% of control values. At lower multiplicities (20 PFU), the rate of inhibition was slower than at high multiplicities. However, at all multiplicities the rates of inhibition of 18S and
28S rRNA remained identical and higher than that of 4S
RNA. (ii) Analysis of
nuclear RNA of cells infected at high multiplicities by
sucrose density gradient centrifugation showed that the synthesis and methylation of
45S rRNA precursor continued at a reduced but significant rate (ca. 30% of control values) at times after
infection when no radioactive
uridine was incorporated or could be chased into 28S and
18S rRNA. This indicates that the inhibition of rRNA synthesis after
herpesvirus infection is a result of two processes: a decrease in the rate of synthesis of 45S
RNA and a decrease in the rate of processing of that 45S
RNA that is synthesized. (iii) Hybridization of nuclear and cytoplasmic
RNA of infected cells with herpesvirus
DNA revealed that a significant proportion of the total
viral RNA in the nucleus has a sedimentation coefficient of 50S or greater. The sedimentation coefficient of virus-specific
RNA associated with cytoplasmic polyribosomes is smaller with a maximum at 16S to 20S, but there is some rapidly sedimenting
RNA (> 28S) here too. (iv) Finally, there was leakage of low-molecular weight (4S)
RNA from infected cells, the leakage being approximately three-fold that of uninfected cells by approximately 5 hr after
infection.