The early phase of Epstein-Barr-Virus (EBV) lytic cycle is characterized by translocation of viral capsid from nucleus to cytoplasm, a process called nuclear egress. We already identified and characterized two EBV proteins required for this process called BFRF1 and BFLF2. BFRF1 interacts with BFLF2 and with nuclear lamin B to form the nuclear egress complex (NEC), moreover it is able to dislocate emerin, an integral nuclear membrane protein that binds nuclear lamina (NL) and is involved in wide range of functions including gene regulation, cell signaling, nuclear and genomic architectural organization. Aim of this project is to investigate if EBV NEC interacts with other cellular proteins involved in nuclear membrane dynamics and the impact of these interactions on EBV nuclear egress as well as on cellular processes . One of these proteins is BAF (Barrier to autointegration factor), we hypothesized that it might mediate viral genome targeting to the NL and the subsequent packaging since it is able to bridge chromosomes to the NL. Moreover we should like to investigate the influence of EBV lytic cycle on LINC complex, a structure localized on the nuclear membrane strictly associated to cytoskeleton, whose signaling is critical for determining cell shape, migration and differentiation. These nuclear structural alterations are strongly associated with various severe human diseases including cancer and increasing evidence reveals that Herpesviruses lytic cycle also plays an important role in the carcinogenic process. Finally the study of these viral-nuclear interactions besides representing a progress in understanding viral biology could shed light on mechanisms important for viral carcinogenesis and could provide a useful model for NL associated pathologies.
Recently it has been shown that BAF regulates gene expression of Herpes Simplex virus (HSV) through an epigenetic mechanism, we think it could be interesting to investigate its possible role in EBV lytic cycle since this could contribute to clarify molecular mechanisms of viral replication. Furthermore, in the last few years there is a growing interest towards this protein since it has been associated not only to DNA replication but also to carcinogenesis and it is considered a possible target for chemiotherapy (Gorjánácz M et al. 2014). EBV lytic cycle is also linked to tumors developments and understanding its interaction with BAF could also be important in this respect and has never been investigated.
Nuclear membrane is a dynamic barrier which is not only strictly mechanical but has also an important role in chromatin dynamic, regulation of gene expression and also in determining cell shape, migration and differentiation. Viral nuclear egress deeply alters nuclear membrane by interaction of its NEC with several proteins, it is important to better characterize these interactions in order to elucidate how lytic cycle works and furthermore how it affects cell phenotype up to pathology. Nuclear membrane alterations in-fact is strongly associated with various severe human diseases (envelopathies) including cancer (Janin et al. 2017). Interactions between EBV replication and LINC complex has never been investigated and might contribute to better understanding of carcinogenesis linked to viral lytic cycle, moreover nuclear egress of Herpesviruses can also provide a useful model for studying nuclear membrane dynamics that can be involved in envelopathies.
References
Gorjánácz M. Nuclear assembly as a target for anti-cancer therapies. Nucleus. 2014 Jan-Feb;5(1):47-55
Janin A, Bauer D, Ratti F, Millat G, Méjat A. Nuclear envelopathies: a complex LINC between nuclear envelope and pathology. Orphanet J Rare Dis. 2017 Aug 30;12(1):147