Characterization of Human Cytomegalovirus UL16 and UL17 Transcripts

Up to now, the UL16-17 region of human cytomegalovirus (HCMV) has not been well characterized at the level of mRNA and protein, especially for the Han strain, the first clinical HCMV strain in China. In previous studies, three transcripts were detected from the UL16-17 region by northern blot analysis for Merlin strain. Transcriptions of UL16 and UL17 were also studied by 5' rapid amplification of cDNA ends (5'RACE) and deep sequencing for AD169 and Towne strains, respectively. However, details of 3' end of UL16 and UL17 transcripts have never been confirmed by 3'RACE. The expressing phage of the UL16-17 region needs further research by northern blot, too. In the present study, cDNA library screening, northern blot and RACE were used to identify the transcription characteristics of the UL16-17 region. Mainly, 3 clusters of transcripts with the same 3' end were found to be expressed from the UL16-17 region in both Han and AD169 strains. The lengths of the core transcripts among the 3 clusters were 1,254nt, 718nt and 468nt, respectively. The corresponding 5' ends are at nt23119, nt23655, nt23905 in the HCMV Han genome. The consistent 3' end is located at nt24372 in the Han genome. The 1,254nt and 468nt transcripts are transcribed in early and late phases, and the 718nt transcript is transcribed only in the late phase.