Regulation of herpesvirus macromolecular synthesis: nuclear retention of nontranslated viral RNA sequences.

We report two instances of selective accumulation of herpes simplex 1 RNA transcripts in different compartments of infected HEp-2 cells. In the first, transcripts derived from about 50% of the viral DNA accumulated in the nuclei of cells 8 hr after infection. However, only 40-42% of the DNA was represented in transcripts accumulating in both cytoplasm and polyribosomes. A more striking disparity in the distribution of transcripts between nuclei and cytoplasm occurred when viral infection was initiated and maintained for several hours in the absence of protein synthesis. RNA complementary to about 50% of the viral DNA accumulated in the nuclei, while transcripts derived from only about 10% of the DNA were detectable in the cytoplasm. The transcripts that were selectively transported in the presence of cycloheximide seem to be functional messenger RNA molecules, since they were found on polysomes immediately after cycloheximide reversal. In contrast, RNA retained in the nuclei during the period of cycloheximide treatment was not mobilized when protein synthesis subsequently resumed. The two instances of selective RNA transport observed during herpesvirus infection suggest that only viral transcripts competent to function in translation are exported from the nucleus.