Kaposi's sarcoma-associated herpesviral IL-6 and human IL-6 open reading frames contain miRNA binding sites and are subject to cellular miRNA regulation.
ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) encodes a viral interleukin 6 (vIL-6) that mimics many activities of human IL-6 (hIL-6). Both vIL-6 and hIL-6 play important roles in stimulating the proliferation of tumours caused by KSHV. Here, we provide evidence that a miRNA pathway is involved in regulation of vIL-6 and hIL-6 expression through binding sites in their open reading frames (ORFs). We show a direct repression of vIL-6 by hsa-miR-1293 and hIL-6 by hsa-miR-608. The repression of vIL-6 by miR-1293 was reversed by disruption of the vIL-6 miR-1293 seed match through the introduction of point mutations. In addition, expression of vIL-6 or hIL-6 in KSHV-infected cells could be enhanced by transfection of the respective miRNA inhibitors. In situ hybridization of human lymph node sections revealed that miR-1293 is primarily expressed in the germinal centre but is deficient in the mantle zone of lymph nodes, where the expression of vIL-6 is often found in patients with KSHV-associated multicentric Castleman's disease, providing evidence of an anatomical correlation. Taking these factors together, our study indicates that IL-6 expression can be regulated by miRNA interactions in its ORF and provides evidence for the role of these interactions in the pathogenesis of KSHV-associated diseases.
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ABSTRACT: All metazoan eukaryotes express microRNAs (miRNAs), roughly 22-nucleotide regulatory RNAs that can repress the expression of messenger RNAs bearing complementary sequences. Several DNA viruses also express miRNAs in infected cells, suggesting a role in viral replication and pathogenesis. Although specific viral miRNAs have been shown to autoregulate viral mRNAs or downregulate cellular mRNAs, the function of most viral miRNAs remains unknown. Here we report that the miR-K12-11 miRNA encoded by Kaposi's-sarcoma-associated herpes virus (KSHV) shows significant homology to cellular miR-155, including the entire miRNA 'seed' region. Using a range of assays, we show that expression of physiological levels of miR-K12-11 or miR-155 results in the downregulation of an extensive set of common mRNA targets, including genes with known roles in cell growth regulation. Our findings indicate that viral miR-K12-11 functions as an orthologue of cellular miR-155 and probably evolved to exploit a pre-existing gene regulatory pathway in B cells. Moreover, the known aetiological role of miR-155 in B-cell transformation suggests that miR-K12-11 may contribute to the induction of KSHV-positive B-cell tumours in infected patients.Nature 01/2008; 450(7172):1096-9. · 38.60 Impact Factor
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ABSTRACT: We show that the microRNA miR-155 can be processed from sequences present in BIC RNA, a spliced and polyadenylated but non-protein-coding RNA that accumulates in lymphoma cells. The precursor of miR-155 is likely a transient spliced or unspliced nuclear BIC transcript rather than accumulated BIC RNA, which is primarily cytoplasmic. By using a sensitive and quantitative assay, we find that clinical isolates of several types of B cell lymphomas, including diffuse large B cell lymphoma (DLBCL), have 10- to 30-fold higher copy numbers of miR-155 than do normal circulating B cells. Similarly, the quantities of BIC RNA are elevated in lymphoma cells, but ratios of the amounts of the two RNAs are not constant, suggesting that the level of miR-155 is controlled by transcription and processing. Significantly higher levels of miR-155 are present in DLBCLs with an activated B cell phenotype than with the germinal center phenotype. Because patients with activated B cell-type DLBCL have a poorer clinical prognosis, quantification of this microRNA may be diagnostically useful.Proceedings of the National Academy of Sciences 04/2005; 102(10):3627-32. · 9.74 Impact Factor
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ABSTRACT: B lymphocytes perform somatic hypermutation and class-switch recombination (CSR) of the immunoglobulin locus to generate an antibody repertoire diverse in both affinity and function. These somatic diversification processes are catalyzed by activation-induced cytidine deaminase (AID), a potent DNA mutator whose expression and function are highly regulated. Here we show that AID was regulated posttranscriptionally by a lymphocyte-specific microRNA, miR-155. We found that miR-155 was upregulated in murine B lymphocytes undergoing CSR and that it targeted a conserved site in the 3'-untranslated region of the mRNA encoding AID. Disruption of this target site in vivo resulted in quantitative and temporal deregulation of AID expression, along with functional consequences for CSR and affinity maturation. Thus, miR-155, which has recently been shown to play important roles in regulating the germinal-center reaction, does so in part by directly downmodulating AID expression.Immunity 06/2008; 28(5):621-9. · 19.80 Impact Factor