Characterization of a major early gene from the human cytomegalovirus long inverted repeat; predicted amino acid sequence of a 30-kDa protein encoded by the 1.2-kb mRNA.

The human cytomegalovirus (CMV) long inverted repeat (TRL:IRL) encodes three major early mRNAs. One of these RNAs is a 1.2-kb transcript that maps between 0.792 and 0.797 map units on the human CMV genome. Primer extension experiments, in addition to nucleotide sequence analyses of cloned cDNA transcripts and human CMV IRL DNA fragments, demonstrated that the 1.2-kb mRNA was not spliced. A single major open reading frame of 254 amino acids was identified, encoding a basic polypeptide of approximately 30 kDa. This polypeptide contains 19% Arg, Lys, and His residues, and would have a net positive charge of 31 at neutral pH. Examination of the deduced amino acid sequence revealed several potential phosphorylation sites and a hydrophobic carboxy terminus which resembles a membrane anchor sequence. In vitro translation of human CMV infected cell RNA, hybrid selected with either cloned cDNA or human CMV IRL DNA fragments specific for the 1.2-kb mRNA, resulted in a unique translation product that migrated on SDS-polyacrylamide gels with an apparent molecular mass of 37 kDa. Potential transcriptional regulatory sequences were also identified upstream of the gene encoding the 30-kDa protein.