Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of the most common neoplasm in untreated AIDS patients, and is also affiliated with two B cell lymphoproliferative disorders. The lytic viral replication cycle has previously been shown to be an essential component of KSHV-induced pathogenesis. One prominent consequence of lytic KSHV infection is a near total destruction of the cellular transcriptome, termed 'host shutoff'. This phenotype is mediated by the viral SOX protein which promotes enhanced cellular messenger RNA (mRNA) degradation, likely via interception of cellular RNA stability pathways. We have identified 2 novel SOX activities linked to host shutoff: SOX induces nuclear re-localization of cytoplasmic poly(A) binding protein (PABPC), and triggers disruption of the 3'end processing of cellular mRNAs in the nucleus leading to their hyperadenylation. PABPC is a cellular protein that plays a key role in mRNA translation and stability in the cytoplasm yet has no known nuclear functions. Thus, we hypothesize that its aberrant localization in SOX-expressing cells is a significant contributor to cytoplasmic mRNA destruction. Within the nucleus, the nascent hyperadenylated cellular mRNAs are not exported, and we predict they are destroyed by cellular quality control mechanisms. Interestingly, we have preliminary data indicating that nuclear PABPC is an important driver of the hyperadenylation phenotype. Thus, KSHV appears to target PABPC to eliminate both nuclear and cytoplasmic cellular messages via distinct mechanisms. This represents a completely novel mechanism of virus-induced termination of host gene expression and, additionally, reveals for the first time in human cells a mechanism for polyadenylation-stimulated mRNA decay and a role for PABPC in the nucleus. Emerging connections between disruption of normal cellular RNA turnover pathways and human disease have highlighted the importance of understanding mechanisms by which such events become deregulated;it is in this regard that KSHV SOX represents an excellent tool to probe how pathogenic human viruses may interface with these critical cellular pathways. This proposal will explore the connections between SOX-induced PABPC import and mRNA hyperadenylation, as well as explore the contribution of cellular quality control pathways towards the ultimate destruction of these messages. Specifically, we will begin by confirming that nuclear PABPC drives hyperadenylation then proceed to dissect the mechanisms by which this occurs. PABPC is a key antagonist of the nonsense-mediated mRNA decay pathway in the cytoplasm, and we will therefore explore the potential aberrant activation of this and other quality control pathways during KSHV infection. Finally, we will monitor the contribution of host shutoff towards viral replication and pathogenesis both in cell culture and in murine models.
Viruses not only cause disease, but are also superb tools to probe the inner workings of our own cells. We investigate how a cancer causing human herpesvirus destroys cellular messages to enhance its own replication, as this information will provide important clues both into how this virus thrives in infected individuals and also how cellular gene expression is regulated.
|Davis, Zoe H; Verschueren, Erik; Jang, Gwendolyn M et al. (2015) Global mapping of herpesvirus-host protein complexes reveals a transcription strategy for late genes. Mol Cell 57:349-60|
|Wong-Ho, Elaine; Wu, Ting-Ting; Davis, Zoe H et al. (2014) Unconventional sequence requirement for viral late gene core promoters of murine gammaherpesvirus 68. J Virol 88:3411-22|
|Abernathy, Emma; Clyde, Karen; Yeasmin, Rukhsana et al. (2014) Gammaherpesviral gene expression and virion composition are broadly controlled by accelerated mRNA degradation. PLoS Pathog 10:e1003882|
|Kronstad, Lisa M; Brulois, Kevin F; Jung, Jae U et al. (2014) Reinitiation after translation of two upstream open reading frames (ORF) governs expression of the ORF35-37 Kaposi's sarcoma-associated herpesvirus polycistronic mRNA. J Virol 88:6512-8|
|Kronstad, Lisa M; Brulois, Kevin F; Jung, Jae U et al. (2013) Dual short upstream open reading frames control translation of a herpesviral polycistronic mRNA. PLoS Pathog 9:e1003156|
|Covarrubias, Sergio; Gaglia, Marta M; Kumar, G Renuka et al. (2011) Coordinated destruction of cellular messages in translation complexes by the gammaherpesvirus host shutoff factor and the mammalian exonuclease Xrn1. PLoS Pathog 7:e1002339|
|Richner, Justin M; Clyde, Karen; Pezda, Andrea C et al. (2011) Global mRNA degradation during lytic gammaherpesvirus infection contributes to establishment of viral latency. PLoS Pathog 7:e1002150|
|Kumar, G Renuka; Shum, Leona; Glaunsinger, Britt A (2011) Importin alpha-mediated nuclear import of cytoplasmic poly(A) binding protein occurs as a direct consequence of cytoplasmic mRNA depletion. Mol Cell Biol 31:3113-25|
|Kumar, G Renuka; Glaunsinger, Britt A (2010) Nuclear import of cytoplasmic poly(A) binding protein restricts gene expression via hyperadenylation and nuclear retention of mRNA. Mol Cell Biol 30:4996-5008|