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The Kaposi's sarcoma-associated herpesvirus K8 protein interacts with CREB-binding protein (CBP) and represses CBP-mediated transcription.

ABSTRACT: Kaposi's sarcoma-associated herpesvirus (KSHV) open reading frame K8 encodes a basic region-leucine zipper protein of 237 amino acids that homodimerizes with its bZIP domain. KSHV K8 shows significant homology to the Epstein-Barr virus (EBV) immediate-early protein Zta, a key regulator in the reactivation and replication of EBV. In this study, we report that K8, like its homolog EBV Zta, interacts with cellular CREB-binding protein (CBP) in vivo and in vitro. This interaction requires the C/H3 domain of CBP and the basic region of K8. K8 represses CBP-mediated transcription by competing with limited amounts of cellular CBP, exemplified by the reduced expression from the AP-1 and human immunodeficiency virus long terminal repeat promoters.

SUBMITTER: Hwang S

PROVIDER: S-EPMC114518 | biostudies-literature | 2001 Oct

REPOSITORIES: biostudies-literature

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The Kaposi's sarcoma-associated herpesvirus K8 protein interacts with CREB-binding protein (CBP) and represses CBP-mediated transcription.

Hwang S S Gwack Y Y Byun H H Lim C C Choe J J

Journal of virology 20011001 19

Kaposi's sarcoma-associated herpesvirus (KSHV) open reading frame K8 encodes a basic region-leucine zipper protein of 237 amino acids that homodimerizes with its bZIP domain. KSHV K8 shows significant homology to the Epstein-Barr virus (EBV) immediate-early protein Zta, a key regulator in the reactivation and replication of EBV. In this study, we report that K8, like its homolog EBV Zta, interacts with cellular CREB-binding protein (CBP) in vivo and in vitro. This interaction requires the C/H3 d ...[more]

PMID: 11533213

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Project description:COX-2 has been implicated in Kaposi's sarcoma-associated herpesvirus (KSHV) latency and pathogenesis (A. George Paul, N. Sharma-Walia, N. Kerur, C. White, and B. Chandran, Cancer Res. 70:3697-3708, 2010; P. P. Naranatt, H. H. Krishnan, S. R. Svojanovsky, C. Bloomer, S. Mathur, and B. Chandran, Cancer Res. 64:72-84, 2004; N. Sharma-Walia, A. G. Paul, V. Bottero, S. Sadagopan, M. V. Veettil, N. Kerur, and B. Chandran, PLoS Pathog. 6:e1000777, 2010; N. Sharma-Walia, H. Raghu, S. Sadagopan, R. Sivakumar, M. V. Veettil, P. P. Naranatt, M. M. Smith, and B. Chandran, J. Virol. 80:6534-6552, 2006). However, the precise regulatory mechanisms involved in COX-2 induction during KSHV infection have never been explored. Here, we identified cis-acting elements involved in the transcriptional regulation of COX-2 upon KSHV de novo infection. Promoter analysis using human COX-2 promoter deletion and mutation reporter constructs revealed that nuclear factor of activated T cells (NFAT) and the cyclic AMP (cAMP) response element (CRE) modulate KSHV-mediated transcriptional regulation of COX-2. Along with multiple KSHV-induced signaling pathways, infection-induced prostaglandin E(2) (PGE(2)) also augmented COX-2 transcription. Infection of endothelial cells markedly induced COX-2 expression via a cyclosporine A-sensitive, calcineurin/NFAT-dependent pathway. KSHV infection increased intracellular cAMP levels and activated protein kinase A (PKA), which phosphorylated the CRE-binding protein (CREB) at serine 133, which probably led to interaction with CRE in the COX-2 promoter, thereby enhancing COX-2 transcription. PKA selective inhibitor H-89 pretreatment strongly inhibited CREB serine 133, indicating the involvement of a cAMP-PKA-CREB-CRE loop in COX-2 transcriptional regulation. In contrast to phosphatidylinositol 3-kinase and protein kinase C, inhibition of FAK and Src effectively reduced KSHV infection-induced COX-2 transcription and protein levels. Collectively, our study indicates that mediation of COX-2 transcription upon KSHV infection is a paradigm of a complex regulatory milieu involving the interplay of multiple signal cascades and transcription factors. Intervention at each step of COX-2/PGE(2) induction can be used as a potential therapeutic target to treat KSHV-associated neoplasm and control inflammatory sequels of KSHV infection.

Project description:Kaposi's sarcoma-associated herpesvirus (KSHV) lytic replication and constant primary infection of fresh cells are crucial for viral tumorigenicity. The virus-encoded bZIP family protein K8 plays an important role in viral DNA replication in both viral reactivation and de novo infection. The mechanism underlying the functional role of K8 in the viral life cycle is elusive. Here, we report that K8 is an RNA binding protein that also associates with many other proteins, including other RNA binding proteins. Many protein-protein interactions involving K8 are mediated by RNA. Using a UV cross-linking and immunoprecipitation (CLIP) procedure combined with high-throughput sequencing, RNAs that are associated with K8 in BCBL-1 cells were identified, including both viral (PAN, T1.4, T0.7, etc.) and cellular (MALAT-1, MRP, 7SK, etc.) RNAs. An RNA binding motif in K8 was defined, and mutation of the motif abolished the ability of K8 to bind to many noncoding RNAs, as well as viral DNA replication during de novo infection, suggesting that the K8 functions in viral replication are carried out through RNA association. The functions of K8 and associated T1.4 RNA were investigated in detail, and the results showed that T1.4 mediates the binding of K8 to ori-Lyt DNA. The T1.4-K8 complex physically bound to KSHV ori-Lyt DNA and recruited other proteins and cofactors to assemble a replication complex. Depletion of T1.4 abolished DNA replication in primary infection. These findings provide mechanistic insights into the role of K8 in coordination with T1.4 RNA in regulating KSHV DNA replication during de novo infection.IMPORTANCE Genomewide analyses of the mammalian transcriptome revealed that a large proportion of sequence previously annotated as noncoding regions is actually transcribed and gives rise to stable RNAs. The emergence of a large number of noncoding RNAs suggests that functional RNA-protein complexes, e.g., ribosomes or spliceosomes, are not ancient relics of the last ribo-organism but would be well adapted to a regulatory role in biology. K8 has been puzzling because of its unique characteristics, such as multiple regulatory roles in gene expression and DNA replication without DNA binding capability. This study reveals the mechanism underlying its regulatory role by demonstrating that K8 is an RNA binding protein that binds to DNA and initiates DNA replication in coordination with a noncoding RNA. It is suggested that many K8 functions, if not all, are carried out through its associated RNAs.

Dataset Information

The Kaposi's sarcoma-associated herpesvirus K8 protein interacts with CREB-binding protein (CBP) and represses CBP-mediated transcription.

Publications

The Kaposi's sarcoma-associated herpesvirus K8 protein interacts with CREB-binding protein (CBP) and represses CBP-mediated transcription.

Similar Datasets

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