Suppression of tetradecanoyl phorbol acetate-induced lytic reactivation of Kaposi's sarcoma-associated herpesvirus by K1 signal transduction.
The K1 protein of Kaposi's sarcoma-associated herpesvirus (KSHV) contains an immunoreceptor tyrosine-based activation motif (ITAM) in its cytoplasmic region and elicits cellular signal transduction through this motif. To investigate the role of K1 signal transduction in KSHV replication, we expressed full-length K1 and CD8-K1 chimeras in BCBL1 cells. Unlike its strong signaling activity in uninfected B lymphocytes, K1 did not induce intracellular calcium mobilization or NF-AT activation at detectable levels in KSHV-infected BCBL1 cells. Instead, K1 signaling dramatically suppressed KSHV lytic reactivation induced by tetradecanoyl phorbol acetate (TPA) stimulation, but not by ORF50 ectopic expression. Mutational analysis showed that the cytoplasmic ITAM sequence of K1 was required for this suppression. Viral microarray and immunoblot analyses demonstrated that K1 signaling suppressed the TPA-mediated increase in the expression of a large subset of viral lytic genes in KSHV-infected BCBL1 cells. Furthermore, electrophoretic mobility shift assays demonstrated that TPA-induced activation of AP-1, NF-kappaB, and Oct-1 activities was severely diminished in BCBL1 cells expressing the K1 cytoplasmic domain. The reduced activities of these transcription factors may confer the observed reduction in viral lytic gene expression. These results demonstrate that K1-mediated signal transduction in KSHV-infected cells is profoundly different from that in KSHV-negative cells. Furthermore, K1 signal transduction efficiently suppresses TPA-mediated viral reactivation in an ITAM-dependent manner, and this suppression may contribute to the establishment and/or maintenance of KSHV latency in vivo.
Lee
Bok-Soo
BS
Department of Microbiology and Molecular Genetics and Division of Tumor Virology, New England Regional Primate Research Center, Harvard Medical School, Southborough, Massachusetts 01772, USA.
Paulose-Murphy
Mini
M
Chung
Young-Hwa
YH
Connlole
Michelle
M
Zeichner
Steven
S
Jung
Jae U
JU
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D016827:CD8 Antigens / Q000235:genetics / Q000378:metabolism; D020013:Calcium Signaling; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D015870:Gene Expression; D005814:Genes, Viral; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism; D019288:Herpesvirus 8, Human / Q000187:drug effects* / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D051863:Host Cell Factor C1; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D050811:Octamer Transcription Factor-1; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014779:Virus Replication
D016827:CD8 Antigens; D004268:DNA-Binding Proteins; D006023:Glycoproteins; C497692:HCFC1 protein, human; D051863:Host Cell Factor C1; C111600:K1 protein, Human herpesvirus 8; C113454:K8.1 protein, Human herpesvirus 8; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D050811:Octamer Transcription Factor-1; C494165:POU2F1 protein, human; D011993:Recombinant Fusion Proteins; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D014764:Viral Proteins; D013755:Tetradecanoylphorbol Acetate