Sensitivity of an epstein-barr virus-positive tumor line, Daudi, to alpha interferon correlates with expression of a GC-rich viral transcript.
The exquisite sensitivity of the Burkitt's lymphoma (BL)-derived cell line Daudi to type I interferons has not previously been explained. Here we show that expression of an Epstein-Barr virus (EBV) transcript, designated D-HIT (Y. Gao et al., J. Virol. 71:84-94, 1997), correlates with the sensitivity of different Daudi cell isolates (or that of other EBV-carrying cells, where known) to alpha interferon (IFN-alpha). D-HIT, transcribed from a GC-rich repetitive region (IR4) of the viral genome, is highly structured, responding to RNase digestion in a manner akin to double-stranded RNA. Comparing EBV-carrying BL cell lines with differing responses to IFN-alpha, we found the protein levels of the dsRNA-activated kinase, PKR, to be similar, whereas the levels of the autophosphorylated active form of PKR varied in a manner that correlated with endogenous levels of D-HIT expression. In a classical in vitro kinase assay, addition of either poly(I)-poly(C) or an in vitro-transcribed D-HIT homolog stimulated the autophosphorylation activity of PKR from IFN-alpha-treated cells in both EBV-positive and EBV-negative B lymphocytes. By transfection experiments, these RNAs were shown to reduce cell proliferation and to sensitize otherwise relatively insensitive Raji cells to IFN-alpha. The data lead to a model wherein the D-HIT viral RNA also serves as a possible transcriptional activator of IFN-alpha or cellular genes regulated by this cytokine.
Gao
Y
Y
Department of Infectious Diseases, Imperial College School of Medicine, London W12 0NN, United Kingdom.
Xue
S a
Sa
Griffin
B E
BE
D001402:B-Lymphocytes / Q000821:virology; D002051:Burkitt Lymphoma / Q000821:virology*; D002455:Cell Division; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D020862:GC Rich Sequence; D005786:Gene Expression Regulation; D004854:Herpesvirus 4, Human; D016898:Interferon-alpha / Q000235:genetics / Q000494:pharmacology*; D009690:Nucleic Acid Conformation; D011070:Poly I-C; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000235:genetics; D012367:RNA, Viral / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured; D019892:eIF-2 Kinase
D016898:Interferon-alpha; D012333:RNA, Messenger; D012367:RNA, Viral; D019892:eIF-2 Kinase; D011070:Poly I-C