Nuclear Lamina binds the EBV genome during latency and regulates viral gene expression

ABSTRACT The Epstein Barr virus (EBV) establishes a persistent latent infection in almost 90% of the population worldwide. EBV latent infection is associated with several malignancies of epithelial and lymphoid origin. In latently infected cells, the EBV genome persists as a chromatinized episome that expresses a limited set of viral genes. Latent genes are expressed in different patterns that are referred to as latency types. Latency types coincide with varying stages of EBV infection and various malignancies. Our previous work demonstrated that latency types correlate with differences in the composition and structure of the EBV episome. Several cellular factors, including nuclear lamina, regulate chromatin composition and chromatin architecture. The interaction with nuclear lamina has already been studied in the context of EBV lytic reactivation. Still, the role of nuclear lamina in controlling EBV latency has not been investigated. Here, we reported that nuclear lamina is also another essential epigenetic regulator of the EBV episome. First, we observed that in B cells, EBV infection affects the composition of nuclear lamina by inducing the expression of Lamin A/C, and Lamin A/C is present only in EBV+ B cells expressing the Type III latency program. By ChIP-seq, we determined that lamins, Lamin B1 and Lamin A/C, bind the EBV genome, and their binding correlates with deposition of the histone repressive mark H3K9me2. By RNA-seq, we observed that the knock-out of Lamin A/C alters EBV gene expression in B cells and decreases H3K9me2 levels across the viral genome. Our data indicate that the interaction between lamins and the EBV episome contributes to the epigenetic control of viral genes expression during latency, suggesting a restrictive function of the nuclear lamina in the host response against the intrusion of viral DNA into the nucleus. AUTHOR SUMMARY Epstein-Barr virus (EBV) is a common herpesvirus that establishes lifelong latent infection in a small fraction of the B cells of infected individuals. In most cases, EBV infection is asymptomatic; however, especially in the context of immune suppression, EBV latent infection is associated with several malignancies. In EBV+ cancer cells, latent viral gene expression plays an essential role in sustaining the cancer phenotype. In previous works, we and others established that epigenetic modifications of the viral genomes are critical to regulating EBV gene expression during latency. Understanding how the EBV genome is epigenetically regulated during latent infection can help us develop new specific therapeutic targets for treating EBV+ malignancies. Nuclear Lamina plays an essential role in regulating the composition and the structure of cellular chromatin. In the present study, we determined that Nuclear Lamina binds the EBV genome during latency, influencing viral gene expression in the present study. Depleting one component of the nuclear lamina, Lamin A/C, increases the expression of latent EBV genes that are usually associated with cellular proliferation, indicating that the binding of the nuclear lamina with the viral genome is essential to control viral gene expression in infected cells. Our data show for the first time that the nuclear lamina may be involved in the cellular response against EBV infection by restricting viral gene expression.