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Functional characterization of Kaposi's sarcoma-associated herpesvirus open reading frame K8 by bacterial artificial chromosome-based mutagenesis.

ABSTRACT: The open reading frame K8 of Kaposi's sarcoma-associated herpesvirus (KSHV) encodes a basic leucine zipper (bZip) protein that binds to the origin of viral DNA replication and is an integral component of viral lytic DNA replication complex. Moreover, K8 physically interacts with replication and transcription activator (RTA) and represses its transactivation activity on several viral promoters. To investigate the role of this protein in viral life cycle, we constructed two K8-null recombinant mutant viruses (BAC-?K8 and BAC-stopK8) by using a bacterial artificial chromosome (BAC) system. Latent viral infection can be reconstituted in 293T and BJAB cells with wild-type and the K8-null recombinant viruses by introducing the cloned viral genomes into the cells. When the cells carrying these viruses were induced with 12-O-tetradecanoylphorbol-13-acetate (TPA) and sodium butyrate, no significant difference was seen in overall viral gene expression between wild-type and K8-null viruses, with lytic DNA replication still active in the latter. However, 293T cells harboring K8-null mutant viruses, either BAC-?K8 or BAC-stopK8, displayed lower copy numbers of latent KSHV genome in comparison with wild-type viruses. Furthermore, although K8 deficiency appeared to not affect infectivity when K8-null viruses were used to infect 293T, primary human microvascular dermal endothelial and human foreskin fibroblast cells, they exhibited much lower viral genome copy numbers in all types of cell compared to wild-type viruses. Taken together, these data suggest a possible role of K8 in abortive lytic DNA replication occurring in early stages of de novo infection or in the maintenance of latent viral genomes.

SUBMITTER: Wang Y

PROVIDER: S-EPMC3067771 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature

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Functional characterization of Kaposi's sarcoma-associated herpesvirus open reading frame K8 by bacterial artificial chromosome-based mutagenesis.

Wang Yan Y Sathish Narayanan N Hollow Charles C Yuan Yan Y

Journal of virology 20101215 5

The open reading frame K8 of Kaposi's sarcoma-associated herpesvirus (KSHV) encodes a basic leucine zipper (bZip) protein that binds to the origin of viral DNA replication and is an integral component of viral lytic DNA replication complex. Moreover, K8 physically interacts with replication and transcription activator (RTA) and represses its transactivation activity on several viral promoters. To investigate the role of this protein in viral life cycle, we constructed two K8-null recombinant mut ...[more]

PMID: 21159864

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Project description:Herpesviruses alternate between the latent and the lytic life cycle. Switching into the lytic life cycle is important for herpesviral replication and disease pathogenesis. Activation of a transcription factor replication and transcription activator (RTA) has been demonstrated to govern this switch in Kaposi's sarcoma-associated herpesvirus (KSHV). The protein encoded by open reading frame 49 from KSHV (ORF49KSHV) has been shown to upregulate lytic replication in KSHV by enhancing the activities of the RTA. We have solved the crystal structure of the ORF49KSHV protein to a resolution of 2.4 Å. The ORF49KSHV protein has a novel fold consisting of 12 alpha-helices bundled into two pseudodomains. Most notably are distinct charged patches on the protein surface, which are possible protein-protein interaction sites. Homologs of the ORF49KSHV protein in the gammaherpesvirus subfamily have low sequence similarities. Conserved residues are mainly located in the hydrophobic regions, suggesting that they are more likely to play important structural roles than functional ones. Based on the identification and position of three sulfates binding to the positive areas, we performed some initial protein-DNA binding studies by analyzing the thermal stabilization of the protein in the presence of DNA. The ORF49KSHV protein is stabilized in a dose-responsive manner by double-stranded oligonucleotides, suggesting actual DNA interaction and binding. Biolayer interferometry studies also demonstrated that the ORF49KSHV protein binds these oligonucleotides. Kaposi's sarcoma-associated herpesvirus (KSHV) is a tumorigenic gammaherpesvirus that causes multiple cancers and lymphoproliferative diseases. The virus exists mainly in the quiescent latent life cycle, but when it is reactivated into the lytic life cycle, new viruses are produced and disease symptoms usually manifest. Several KSHV proteins play important roles in this reactivation, but their exact roles are still largely unknown. In this study, we report the crystal structure of the open reading frame 49 protein encoded by KSHV (ORF49KSHV). Possible regions for protein interaction that could harbor functional importance were found on the surface of the ORF49KSHV protein. This led to the discovery of novel DNA binding properties of the ORF49KSHV protein. Evolutionary conserved structural elements with the functional homologs of ORF49KSHV were also established with the structure.

Dataset Information

Functional characterization of Kaposi's sarcoma-associated herpesvirus open reading frame K8 by bacterial artificial chromosome-based mutagenesis.

Publications

Functional characterization of Kaposi's sarcoma-associated herpesvirus open reading frame K8 by bacterial artificial chromosome-based mutagenesis.

Similar Datasets

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