Expression of Kaposi's sarcoma-associated herpesvirus G protein-coupled receptor monocistronic and bicistronic transcripts in primary effusion lymphomas.

Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) encodes a G protein-coupled receptor (vGPCR) in open reading frame (ORF) 74, which is homologous to human chemokine receptors. KSHV vGPCR is constitutively active and induces VEGF-mediated angiogenesis. Previous studies have shown that ORF 74 is transcribed as part of a bicistronic message containing ORF K14 upstream of ORF 74, with an early lytic pattern of expression. We have now extended these studies by analyzing three different KSHV-positive primary effusion lymphoma (PEL) cell lines and three PEL clinical samples. In addition, we have identified another less abundant monocistronic transcript containing only ORF 74. Both transcripts were identified at low but similar levels in two PEL clinical samples. We evaluated the degree of sequence and functional conservation of ORF74 in three additional PELs and two KS clinical specimens, demonstrating complete identity at the amino acid level among all isolates. While it is expressed as an early lytic transcript in PEL cell lines, in primary clinical PEL samples transcription of KSHV vGPCR can be readily detected.