Marek's disease virus latency-associated transcripts belong to a family of spliced RNAs that are antisense to the ICP4 homolog gene

Marek's disease virus (MDV) latency-associated transcripts include at least two MDV small RNAs (MSRs) and a 10-kb RNA which map antisense to the ICP4 homolog gene and are relatively abundant in MDV-transformed lymphoblastoid cells. This report further describes the biological and structural properties of these RNAs. First, these RNAs were detected in primary lymphomas isolated from chickens infected with several oncogenic MDV strains. Second, the MSRs are nonpolyadenylated, whereas, the 10-kb RNA is predominantly polyadenylated. Third, MSRs localize to the nuclei of both lymphoblastoid cells and cytolytically infected chicken embryo fibroblasts. Fourth, the 3'-region splice junctions of the MSRs during latent and productive infection were determined by sequencing RNA-PCR products generated with primers that flank the 3' splice region. The MSRs contain at least three introns, the largest of which overlaps the ICP4 putative translational start site. Fifth, the 5' end of the MSRs initiates approximately 5 kb upstream from the main body of the RNA. The extreme 5' exon is approximately 251 nucleotides (nt) long and is joined to the main body of the transcript upon removal of a 4,852-nt intron. Finally, the 10-kb RNA lies entirely within the repeats flanking the unique short region of the genome. We believe that the MSRs and 10-kb RNA belong to a family of spliced RNAs that map antisense to the ICP4 gene and comprise a complex transcriptional unit expressed during MDV-induced T-cell transformation