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Lytic but not latent infection by Kaposi's sarcoma-associated herpesvirus requires host CSL protein, the mediator of Notch signaling.

ABSTRACT: Infection by Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) is a key factor in the development of KS. Both latent and lytic KSHV infection is observed in KS tumor cells, and both genetic programs contribute importantly to KS pathogenesis. The viral replication and transcription activator (RTA) protein is a transcription factor that controls the switch from latency to lytic replication. We have previously shown that RTA can activate the expression of several lytic viral genes in transfected cells by interaction with recombination signal sequence-binding protein-J kappa (RBP-J kappa, also called CSL), which in uninfected cells is a transcriptional repressor that is the target of the Notch-signaling pathway. The recognition that many KSHV lytic genes, including RTA itself, contain RBP-J kappa-binding sites raised the possibility that RBP-J kappa-mediated repression may be central to the establishment of latency. Here, we have tested this hypothesis by examining KSHV infection of RBP-J kappa-null murine fibroblasts. Our results show that KSHV latency is efficiently induced in such cells; however, the reactivation of lytic gene expression, viral DNA replication, and the release of progeny viruses are dramatically inhibited in the absence of RBP-J kappa. RBP-J kappa-mediated repression is therefore not essential for establishment of latent infection, but the RTA-mediated redirection of RBP-J kappa activity from repression to activation is critical for lytic viral replication.

SUBMITTER: Liang Y

PROVIDER: S-EPMC166256 | biostudies-other | 2003 Jul

REPOSITORIES: biostudies-other

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Project description:UnlabelledKaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of commonly fatal malignancies of immunocompromised individuals, including primary effusion lymphoma (PEL) and Kaposi's sarcoma (KS). A hallmark of all herpesviruses is their biphasic life cycle-viral latency and the productive lytic cycle-and it is well established that reactivation of the KSHV lytic cycle is associated with KS pathogenesis. Therefore, a thorough appreciation of the mechanisms that govern reactivation is required to better understand disease progression. The viral protein replication and transcription activator (RTA) is the KSHV lytic switch protein due to its ability to drive the expression of various lytic genes, leading to reactivation of the entire lytic cycle. While the mechanisms for activating lytic gene expression have received much attention, how RTA impacts cellular function is less well understood. To address this, we developed a cell line with doxycycline-inducible RTA expression and applied stable isotope labeling of amino acids in cell culture (SILAC)-based quantitative proteomics. Using this methodology, we have identified a novel cellular protein (AT-rich interacting domain containing 3B [ARID3B]) whose expression was enhanced by RTA and that relocalized to replication compartments upon lytic reactivation. We also show that small interfering RNA (siRNA) knockdown or overexpression of ARID3B led to an enhancement or inhibition of lytic reactivation, respectively. Furthermore, DNA affinity and chromatin immunoprecipitation assays demonstrated that ARID3B specifically interacts with A/T-rich elements in the KSHV origin of lytic replication (oriLyt), and this was dependent on lytic cycle reactivation. Therefore, we have identified a novel cellular protein whose expression is enhanced by KSHV RTA with the ability to inhibit KSHV reactivation.ImportanceKaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of fatal malignancies of immunocompromised individuals, including Kaposi's sarcoma (KS). Herpesviruses are able to establish a latent infection, in which they escape immune detection by restricting viral gene expression. Importantly, however, reactivation of productive viral replication (the lytic cycle) is necessary for the pathogenesis of KS. Therefore, it is important that we comprehensively understand the mechanisms that govern lytic reactivation, to better understand disease progression. In this study, we have identified a novel cellular protein (AT-rich interacting domain protein 3B [ARID3B]) that we show is able to temper lytic reactivation. We showed that the master lytic switch protein, RTA, enhanced ARID3B levels, which then interacted with viral DNA in a lytic cycle-dependent manner. Therefore, we have added a new factor to the list of cellular proteins that regulate the KSHV lytic cycle, which has implications for our understanding of KSHV biology.

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Lytic but not latent infection by Kaposi's sarcoma-associated herpesvirus requires host CSL protein, the mediator of Notch signaling.

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