A Rhesus Macaque Rhadinovirus Related to Kaposi’s Sarcoma-Associated Herpesvirus/Human Herpesvirus 8 Encodes a Functional Homologue of Interleukin-6

ABSTRACT The rhesus rhadinovirus strain 17577 (RRV strain 17577) genome is essentially colinear with human herpesvirus 8 (HHV8)/Kaposi’s sarcoma-associated herpesvirus (KSHV) and encodes several analogous open reading frames (ORFs), including the homologue of cellular interleukin-6 (IL-6). To determine if the RRV IL-6-like ORF (RvIL-6) is biologically functional, it was expressed either transiently in COS-1 cells or purified from bacteria as a glutathioneS-transferase (GST)-RvIL-6 fusion and analyzed by IL-6 bioassays. Utilizing the IL-6-dependent B9 cell line, we found that both forms of RvIL-6 supported cell proliferation in a dose-dependent manner. Moreover, antibodies specific to the IL-6 receptor (IL-6R) or the gp130 subunit were capable of blocking the stimulatory effects of RvIL-6. Reciprocal titrations of GST-RvIL-6 against human recombinant IL-6 produced a more-than-additive stimulatory effect, suggesting that RvIL-6 does not inhibit but may instead potentiate normal cellular IL-6 signaling to B cells. These results demonstrate that RRV encodes an accessory protein with IL-6-like activity.

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Kaposi's Sarcoma-Associated Herpesvirus/Human Herpesvirus 8 Transcriptional Activator Rta Is an Oligomeric DNA-Binding Protein That Interacts with Tandem Arrays of Phased A/T-Trinucleotide Motifs

Journal of Virology ◽

10.1128/jvi.77.17.9399-9411.2003 ◽

2003 ◽

Vol 77 (17) ◽

pp. 9399-9411 ◽

Cited By ~ 32

Author(s):

Wei Liao ◽

Yong Tang ◽

Yu-liang Kuo ◽

Bao-Ying Liu ◽

Chi-Jie Xu ◽

...

Keyword(s):

Kaposi's Sarcoma ◽

Human Herpesvirus ◽

Transcriptional Activator ◽

Kaposi’S Sarcoma ◽

Viral Reactivation ◽

Human Herpesvirus 8 ◽

Dependent Manner ◽

Herpesvirus 8 ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma associated herpesvirus (KSHV)/human herpesvirus 8 (HHV-8) encodes an immediate early transcriptional activator, Rta, which mediates viral reactivation from latency and lytic viral replication. Here we report the purification and characterizations of HHV-8 Rta and its interaction with Rta-responsive DNA elements. The Rta response element (RtaRE) in the promoter of the KSHV/HHV-8 K8 open reading frame was mapped to a 47-bp sequence (RtaRE1) and a 60-bp sequence (RtaRE2) upstream of the TATA motif. A comparison of the K8 RtaREs with other viral RtaREs revealed a pattern of multiple A/T triplets spaced with a periodicity of 10 or 20 bp. Substitutions of the in-phase A/T trinucleotides of the RtaRE1 with G/C bases greatly diminished Rta responsiveness and Rta binding. By contrast, base substitutions in an out-of-phase A/T-trinucleotide sequence had no effect. Importantly, multimers of (A/T)3N7 and N5(A/T)5N6(A/T)4 motifs supported a strong Rta response in a copy number-dependent manner. No specific sequence motifs in the spacer regions could be discerned. Potent Rta response, however, was obtained with phased A/T trinucleotides with 7-bp spacers of arbitrary sequences with high G/C content. Lengthening of the phased A/T motifs or lowering of the G/C content of the spacers resulted in a reduction in Rta response. Finally, Escherichia coli-derived Rta is an oligomer of 440 kDa in molecular size and binds RtaRE as an oligomer. These results support a model of Rta transactivation wherein the subunits of the Rta oligomer make multiple contacts with a tandem array of phased A/T triplets in the configuration of (A/T)3(G/C)7 repeats.

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Transcriptional Regulation of the Interleukin-6 Gene of Human Herpesvirus 8 (Kaposi's Sarcoma-Associated Herpesvirus)

Journal of Virology ◽

10.1128/jvi.76.16.8252-8264.2002 ◽

2002 ◽

Vol 76 (16) ◽

pp. 8252-8264 ◽

Cited By ~ 98

Author(s):

Hongyu Deng ◽

Moon Jung Song ◽

Julia T. Chu ◽

Ren Sun

Keyword(s):

Gene Expression ◽

Interleukin 6 ◽

Kaposi's Sarcoma ◽

Human Herpesvirus ◽

Kaposi’S Sarcoma ◽

Human Herpesvirus 8 ◽

Herpesvirus 8 ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Responsive Element ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Human herpesvirus 8 (HHV-8; Kaposi's sarcoma-associated herpesvirus is linked to Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD), all of which are viewed as cytokine-driven malignancies. In particular, interleukin-6 (IL-6) has been found to promote the growth and proliferation of cells from KS and PEL. HHV-8 encodes a homologue of IL-6 (viral IL-6 [vIL-6]), which functions similarly to the cellular IL-6. Therefore, vIL-6 has been proposed to play an important role in tumor progression. Several groups have reported that vIL-6 is expressed from the HHV-8 genome at higher levels in PEL and MCD lesions than in KS lesions. However, it is not clear how vIL-6 expression is regulated. We characterized the transcription at the vIL-6 gene locus by Northern blot analysis and, in contrast to previous reports, we observed two distinct transcripts from induced PEL cell lines. This observation was confirmed by primer extension, as well as 5′ and 3′ rapid amplification of cDNA ends. Two transcription initiation sites and putative TATA boxes were mapped. A luciferase reporter system was used to show that each of the two putative TATA boxes contributed to vIL-6 promoter activity. Since virally encoded transcriptional activator Rta potently activates the viral lytic gene expression cascade, we examined the role of Rta in controlling vIL-6 gene expression and found that Rta activated the vIL-6 promoter. The Rta-responsive element was further mapped through a series of deletion constructs. Electrophoretic mobility shift assays demonstrated that Rta binds directly to the vIL-6 Rta-responsive element, and the core Rta-responsive element was mapped to a 26-bp region spanning from nucleotide 18315 to 18290 on the viral genome. We propose that the existence of two vIL-6 promoters offers opportunities for differential regulation of vIL-6 gene expression in different tissue types and may account for the variable vIL-6 levels observed in KS, PEL, and MCD.

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