Novel, nonconsensus cellular splicing regulates expression of a gene encoding a chemokine-like protein that shows high variation and is specific for human herpesvirus 6

There are few genes that are specific and diagnostic for human herpesvirus- 6. U83 and U22 are two of them. U22 is unique, whereas U83 encodes distant similarity with some cellular chemokines. Reverse transcription-polymerase chain reaction, cDNA cloning, and sequence analyses show polyadenylated RNA transcripts corresponding to minor full-length and abundant spliced forms of U83 in human herpesvirus 6-infected cells. The splice donor and acceptor sites do not fit consensus sequences for either major GT-AG or minor AT-AC introns. However, the spliced form can also be detected in a U83 transfect ed cell line; thus the novel sites are used by cellular mechanisms. This in tron may represent a new minor CT-AC splicing class. The novel splicing reg ulates gene expression by introducing a central stop codon that abrogates p roduction of the chemokine-like molecule, resulting in an encoded truncated peptide. The use of metabolic inhibitors and an infection time course show ed expression of the two RNA transcripts with immediate early kinetics. How ever, the full-length product accumulated later, dependent on virus DNA rep lication, similar to U22. Sequence analyses of 16 strains showed high varia tion (13%) in U83,with conservation of the novel splice sites. Representati ve strain Variants had similar kinetics of expression and spliced products, (C) 1999 Academic Press.