The Translesion Polymerase Pol η Is Required for Efficient Epstein-Barr Virus Infectivity and Is Regulated by the Viral Deubiquitinating Enzyme BPLF1

Abstract

Epstein-Barr virus (EBV) infection and lytic replication are known to induce a cellular DNA damage response. We previously showed that the virally encoded BPLF1 protein interacts with and regulates several members of the translesion synthesis (TLS) pathway, a DNA damage tolerance pathway, and that these cellular factors enhance viral infectivity. BPLF1 is a late lytic cycle gene, but the protein is also packaged in the viral tegument, indicating that BPLF1 may function both early and late during infection. The BPLF1 protein expresses deubiquitinating activity that is strictly conserved across the ; mutation of the active site cysteine results in a loss of enzymatic activity. Infection with an EBV BPLF1 knockout virus results in decreased EBV infectivity. Polymerase eta (Pol η), a specialized DNA repair polymerase, functions in TLS and allows for DNA replication complexes to bypass lesions in DNA. Here we report that BPLF1 interacts with Pol η and that Pol η protein levels are increased in the presence of functional BPLF1. BPLF1 promotes a nuclear relocalization of Pol η molecules which are focus-like in appearance, consistent with the localization observed when Pol η is recruited to sites of DNA damage. Knockdown of Pol η resulted in decreased production of infectious virus, and further, Pol η was found to bind to EBV DNA, suggesting that it may allow for bypass of damaged viral DNA during its replication. The results suggest a mechanism by which EBV recruits cellular repair factors, such as Pol η, to sites of viral DNA damage via BPLF1, thereby allowing for efficient viral DNA replication. Epstein-Barr virus is the causative agent of infectious mononucleosis and infects approximately 90% of the world's population. It causes lymphomas in individuals with acquired and innate immune disorders and is strongly associated with Hodgkin's lymphoma, Burkitt's lymphoma, diffuse large B-cell lymphomas, nasopharyngeal carcinoma (NPC), and lymphomas that develop in organ transplant recipients. Cellular DNA damage is a major determinant in the establishment of oncogenic processes and is well studied, but there are few studies of endogenous repair of viral DNA. This work evaluates how EBV's BPLF1 protein and its conserved deubiquitinating activity regulate the cellular DNA repair enzyme polymerase eta and recruit it to potential sites of viral damage and replication, resulting in enhanced production of infectious virus. These findings help to establish how EBV enlists and manipulates cellular DNA repair factors during the viral lytic cycle, contributing to efficient infectious virion production.

BGLF2 Increases Infectivity of Epstein-Barr Virus by Activating AP-1 upon De Novo Infection

“…For example, the herpes simplex virus (HSV) VP16 protein functions as an efficient transcriptional coactivator of viral IE genes by binding to the host cell factor/octamer-binding protein 1 (HCF/OCT-1) complex ( 5 ). The EBV BPLF1 tegument gene, encoding a deubiquitinase, targets several signaling molecules and replication factors and increases viral amplification ( 6 – 9 ). EBV EBNA2 interacts with recombination signal binding protein suppressor of hairless (RBPJκ) and activates Notch signaling ( 10 ).…”

EBV Genome Mutations and Malignant Proliferations

“…The DUB activity is carried by the first 246 aa of the N-terminal region, and the C61 residue EBV Genome Mutations and Malignant Proliferations DOI: http://dx.doi.org/10.5772/intechopen.93194 of the catalytic triad (Cys-His-Asp) is essential for activity [103]. BPLF1 relocalizes Pol to nuclear sites of viral DNA production, thereby bypassing DNA damage [105]. This mechanism contributes to efficient production of infectious virus.…”

Viral Ubiquitin and Ubiquitin-Like Deconjugases—Swiss Army Knives for Infection

“…The EBV-encoded BPLF1 [ 97 ] and HSV-1-encoded UL36 [ 92 ] were shown to de-ubiquitinate PCNA and to prevent the formation of PCNA foci. In addition, BPLF1 was shown to interact with and to promote the accumulation of the PCNA ligase RAD18 [ 100 ] and translesion synthesis polymerase Polη [ 174 ]. Taken together, these findings point to an important role of the viral deconjugase in regulating the stability, localization and activity of a variety of cellular factors that are recruited at the site of viral replication to assist or counteract the production of infectious virus.…”