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-c oupled receptor (vGPCR) in open reading frame (ORF) 74, which is homologous to human chemokine receptors. KSHV vGPCR is constitutively active and indu ces 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 th ese studies by analyzing three different KSHV-positive primary effusion lym phoma (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 P EL clinical samples. We evaluated the degree of sequence and functional con servation 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 p rimary clinical PEL samples transcription of KSHV vGPCR can be readily dete cted. (C) 2001 Academic Press.