Interaction of Marek's disease virus oncoprotein Meq with heat-shock protein 70 in lymphoid tumour cells

Abstract

Marek's disease virus (MDV) is a highly oncogenic alphaherpesvirus that induces the rapid onset of T-cell lymphomas in poultry. The MDV-encoded oncoprotein Meq plays an important role in oncogenicity, as its deletion abolishes the ability of the virus to induce tumours. It has been shown previously that Meq oncogenicity is linked to its interaction with C-terminal binding protein 1 (CtBP), a property also shared by other virus-encoded oncoproteins such as adenovirus E1A and Epstein-Barr virus EBNA3A and -3C. Therefore, this study examined whether Meq also shares the properties of these viral oncoproteins in interacting with other binding partners such as heatshock protein 70 (Hsp70), a molecular chaperone protein linked to multiple cellular functions including neoplastic transformation. Confocal microscopic analysis demonstrated that MDV infection induced nuclear accumulation of Hsp70 and its co-localization with Meq. Biochemical evidence of Meq-Hsp70 interaction was obtained by two-way immunoprecipitation with Meqand Hsp70-specific antibodies. To demonstrate further the Meq-Hsp70 interaction in virusinduced lymphomas, recombinant MDV was generated expressing an N-terminal tandem affinity purification (TAP) tag-fused Meq by mutagenesis of the infectious BAC clone of the oncogenic MDV strain RB-1B. Demonstration of Hsp70 in the TAP-tag affinity purified Meq from tumours induced by the recombinant virus, using quadrupole time-of-flight tandem mass spectrometry analysis, further confirmed the Meq-Hsp70 interaction in the transformed lymphocytes. Given the well-documented evidence of the tumorigenic properties of Hsp70 and its interaction with a number of other known viral oncoproteins, demonstration of the interaction of Meq and Hsp70 is significant in MDV oncogenesis. INTRODUCTIONCurrent estimates suggest that viruses are involved in 15-20 % of human cancers worldwide (Javier & Butel, 2008). Oncogenic viruses, as efficient inducers of cancers, have helped significantly in understanding the molecular mechanisms of oncogenesis. Marek's disease (MD), a highly oncogenic viral disease induced by Marek's disease virus (MDV), is widely seen as a natural model for virusinduced lymphomas (Calnek, 1986;Osterrieder et al., 2006). MDV induces rapid-onset CD4 + T-cell lymphomas within a few weeks of infection, and MD lymphomas have many biological parallels with tumours associated with human herpesviruses such as Epstein-Barr virus (EBV) and Kaposi's sarcoma herpesvirus (KSHV, human herpesvirus 8). For example, it has recently been shown that MDV and KSHV both encode an oncogenic microRNA-155 orthologue (Gottwein et al., 2007;Zhao et al., 2009), whilst EBV strongly induces host microRNA-155 expression (Yin et al., 2008). However, the most important viral gene associated with MD oncogenicity is Meq (MDV EcoRI Q), encoded from the repeat region (IR L /TR L ) of the MDV genome (Jones et al., 1992;Nair & Kung, 2004). The direct role of Meq in MDV oncogenicity has been clearly demonstrated by the abolition of oncogenicity in Meq-de...

Nuclear Factor kappa B is central to Marek’s Disease herpesvirus induced neoplastic transformation of CD30 expressing lymphocytes in-vivo

“…In our work from MD lymphocytes in vivo, BCL2 protein was unchanged suggesting that any BCL2 functional-deregulation may occur prior to the CD30 lo to CD30 hi transition in the lymphoma environment. HSP70 inhibits both the intrinsic and the extrinsic PCD mechanisms and is frequently increased in malignant tumors [47-50], Meq also co-localizes with HSP70 in the nucleus [49] where HSP70 mediates Meq’s interaction with TP53 and CDK2 [49]. In agreement, we found HSP70 protein was increased and was 100% nuclear.…”

Functional Regulation of an Autographa californica Nucleopolyhedrovirus-Encoded MicroRNA, AcMNPV-miR-1, in Baculovirus Replication

“…These three HSPs were originally shown to defend against infection but have recently been demonstrated to support virus replication and assembly via interactions with viral proteins (44)(45)(46)(47). Thus, by interacting with HSPs, Ac18 may act as a moderator of HSP-associated virus-host interplay (48)(49)(50). The HSPs themselves may play defensive roles; however, with the appearance of Ac18, their roles may become advantageous for the virus.…”

Critical Role of the Virus-Encoded MicroRNA-155 Ortholog in the Induction of Marek's Disease Lymphomas

“…Marek's disease (MD), a naturally occurring neoplastic disease of poultry [8], is an excellent model for herpesvirus-induced lymphomas [9], [10], [11], [12]. All birds exposed to the causative Marek's disease virus (MDV), unless protected by vaccination or have genetic resistance to the disease, develop rapid-onset T-cell lymphomas usually from 3–4 weeks after infection.…”