Transcriptional features and transcript structure of UL145 in different strains of human cytomegalovirus.

The human cytomegalovirus UL145 gene is located between the highly variable genes UL144 and UL146 in the UL/b' region. However, unlike its neighboring genes, UL145 is relatively conserved among strains isolated from patients. The transcriptional features and transcript structure of UL145 has not yet been examined. In this study, the transcriptional features and structure of UL145 were characterized using RNA preparations from three HCMV strains isolated from patients, designated H, C, and X, respectively. Two transcripts were identified by cDNA library screening. Two main clusters of transcripts, one located between 500 and 700 nt, and the other between 1,400 and 1,700 nt, were confirmed by Northern blot analysis. Abundant transcripts were detected at 96 h post-infection by Northern blot, suggesting that UL145 was a late gene. The terminal sequences of transcripts obtained by 3' rapid amplification of cDNA ends demonstrated the presence of polyadenylation. Transcripts identified in the RNA of H, C, and X strains 96 h post-infection had the same 3' end but different 5' ends. In addition to polycistronic transcripts with upstream genes, UL145 could be transcribed as a single transcript during late strain infections.