SPLICED TRANSCRIPTS OF HUMAN CYTOMEGALOVIRUS

The availability of the human cytomegalovirus (HCMV) genomic sequence has resulted in more extensive knowledge of the overall coding capacit y of the virus. Using polymerase chain reaction and rapid sequencing t echniques, we have studied the splicing of mRNAs from a number of the predicted open reading frames (ORFs). Splicing was found between the U L122(IE2) ORF present within major immediate-early (MIE) region 2 and the downstream ORF (UL118) predicted to encode an incomplete glycoprot ein. This locates the IE2 3' donor site and provides evidence of a lin k between the MIE region and downstream ORFs. The downstream UL119-UL1 18-UL115 ORFs also undergo differential splicing, further increasing t he known complexity of this region of the genome. A detailed map of th e differential splicing within the region encoding the MIE ORF is pres ented. Also described are several previously unidentified spliced ORFs found in the long repeats and long unique regions, including one enco ding a transcript with a large (4-kb) intron. The results show that sp liced transcripts are encoded from throughout the genome at immediate- early, early, and late times postinfection.