Latency-associated sense transcripts are expressed during in vitro human cytomegalovirus productive infection

Published studies have identified novel sense transcripts in latent human cytomegalovirus (HCMV) infection. These cytomegalovirus latency-associated transcripts (CLTs) have start sites upstream from the MIE gene productive start site (PSS). We evaluated the expression of the sense CLTs in an in vitro HCMV productive infection. Transcripts with initiation sites upstream from the PSS were detected in infected human fibroblasts using reverse transcription-polymerase chain reaction and 5' rapid amplification of cDNA ends (RACE) analysis. DNA sequencing of 5' RACE PCR products confirmed that the start sites were consistent with sense CLT expression. Furthermore, ribonuclease protection assay analysis showed that transcripts initiating at the latent start site-1 were most abundant at late times postinfection after transcription from the PSS had decreased. In addition, transcription consistent with sense CLT expression was identified in HCMV-infected dTHP-1 cells, monocyte-derived macrophages, and endothelial cells, as well as in clinical isolate-infected human fibroblasts. These findings clearly demonstrate the expression of sense CLTs during in vitro HCMV infection.