Temporal Regulation of Herpes Simplex Virus Type 1UL24mRNA Expression via Differential Polyadenylation

AbstractUsing Northern blot, primer extension, and S1 nuclease analyses of wild-type and deletion-containing herpes simplex type 1 viruses, we found thatUL24sequences are contained in six different transcripts that originate from three previously identified mRNA start sites. Thus, the sixUL24transcripts represent three different pairs of 5′ coterminal mRNAs. Each transcript pair consists of a short species whose 3′ end corresponds to a polyadenylation signal located just downstream of theUL24open reading frame, and a longer species whose 3′ end corresponds to a polyadenylation signal located downstream of theUL26gene. Maximal accumulation of the shortUL24transcripts was at early times during infection, while accumulation of the longer species did not decrease at late times. Consistent with early kinetics, the short transcripts were less sensitive to drugs that inhibited viral DNA replication than the longer transcripts which exhibited leaky–late kinetics. Quantitative S1 nuclease analysis indicated that 3′ ends corresponding to theUL24polyadenylation site were significantly more abundant at early times than at late times. Thus, differential polyadenylation determines the kinetics of accumulation of differentUL24transcripts