KSHV RTA Abolishes NF Kappa B Responsive Gene Expression during Lytic Reactivation by Targeting vFLIP for Degradation via the Proteasome: e91359

• Published in: PloS one Vol. 9; no. 3
• Main Authors: Ehrlich, Elana S, Chmura, Jennifer C, Smith, John C, Kalu, Nene N, Hayward, Gary S
• Format: Journal Article
• Language: English
• Published: 01.03.2014
• Subjects: Herpesvirus; Kaposi's sarcoma-associated herpesvirus
• ISSN: 1932-6203
• DOI: 10.1371/journal.pone.0091359

Kaposi's sarcoma herpesvirus (KSHV) is a gamma-2 herpesvirus present in all cases of Kaposi's sarcoma, primary effusion lymphoma (PEL), and some cases of multicentric Castleman's disease. Viral FLICE inhibitory protein (vFLIP) is a latently expressed gene that has been shown to be essential for survival of latently infected PEL cells by activating the NF Kappa B pathway. Inhibitors of either vFLIP expression or the NF[kgreen]B pathway result in enhanced lytic reactivation and apoptosis. We have observed a decrease in vFLIP protein levels and of NF Kappa B activation in the presence of the KSHV lytic switch protein RTA. Whereas vFLIP alone induced expression of the NF[kgreen]B responsive genes ICAM1 and TNF alpha , inclusion of RTA decreased vFLIP induced ICAM1 and TNF alpha expression in both co-transfected 293T cells and in doxycycline induced TREx BCBL1 cells. RTA expression resulted in proteasome dependent destabilization of vFLIP. Neither RTA ubiquitin E3 ligase domain mutants nor a dominant-negative RAUL mutant abrogated this effect, while RTA truncation mutants did, suggesting that RTA recruits a novel cellular ubiquitin E3 ligase to target vFLIP for proteasomal degradation, allowing for inhibition of NF[kgreen]B responsive gene expression early during lytic reactivation.