Varicella-Zoster Virus ORF49 Functions in the Efficient Production of Progeny Virus through Its Interaction with Essential Tegument Protein ORF44

Abstract

e The ORF49 tegument protein of varicella-zoster virus (VZV) is one of the core gene products that is conserved among herpesvirus family members. Although ORF49 is known to be a cell-tropic factor, its detailed functions remain elusive. ORF44 is another core gene product reported to be essential, although its characterization and detailed functional analysis have not been reported. These two core gene products form a complex in other herpesviruses beyond the host species and herpesvirus subfamilies. Here, we show that complex formation between ORF44 and ORF49 is conserved in VZV. We serendipitously found that binding is eliminated by an amino acid substitution at position 129 (phenylalanine 129), and four amino acids in the carboxyl-terminal half of the acidic cluster in ORF49 (i.e., aspartate-phenylalanine-aspartate-glutamate from positions 41 to 44 [41DFDE44]) were identified as its binding motif. Alanine substitutions in each domain rendered the ORF44F129A mutation lethal for VZV, similar to deletion of the entire ORF44. The phenotype of the ORF49-41AAAA44 mutation was comparable to that of the ORF49-defective virus, including small-plaque formation, impaired growth, and low infectious virus production. These results suggest that the interaction between ORF44 and ORF49 is essential for their role in VZV infection and that ORF49 is required for the efficient production of infectious progeny virus mediated by the conserved interaction between the two proteins.

Epstein-Barr Virus (EBV) Tegument Protein BGLF2 Promotes EBV Reactivation through Activation of the p38 Mitogen-Activated Protein Kinase

“…BGLF2 interacts with NIMA-related protein kinase (NEK9) and GEM-interacting protein (GMIP), induces expression of p21, and induces cell cycle arrest at the G 1 /S transition (43). Several orthologs of BGLF2, such as Kaposi's sarcoma-associated herpesvirus ORF33 (44), varicella-zoster virus ORF44 (45,46), and cytomegalovirus (CMV) UL94 (47), are essential for virus replication; however, herpes simplex virus UL16 is not essential for replication, but deletion of the gene impairs virus growth (48,49). HSV UL16 is important for DNA encapsidation and virus assembly (50,51), and CMV UL94 is required for secondary envelopment of nucleocapsids in the endoplasmic reticulum and the Golgi apparatus (47).…”

In vitro system using human neurons demonstrates that varicella-zoster vaccine virus is impaired for reactivation, but not latency

“…The VZV POka was kindly provided by Michiaki Takahashi (Osaka University, Suita, Osaka, Japan), and VOka (Zostavax) was purchased from Merck. Viruses were propagated on MRC-5 cells, and cell-free virus was prepared as previously described (22); cells were disrupted using a Misonix sonicator 3000.…”

Cytotoxic and immunogenic mechanisms of recombinant oncolytic poliovirus

“…These affect an IRES region coordinating assembly and/or function of ribonucleoprotein complexes (RNPs) containing canonical translation factors (eukaryotic initiation factor (eIF) 4G, eIF4A, eIF4B; [18,19]) and, possibly, accessory IRES trans -acting factors (ITAFs; e.g. poly(rC) binding protein 2 (PCBP2); Ser-Arg (SR) rich protein 20 (SRp20); [18–22]) [23,24]. The IRES RNP recruits 40S ribosomal subunits (e.g.…”

“…The IRES RNP recruits 40S ribosomal subunits (e.g. via eIF4G and eIF3; or -alternatively- via a mechanism involving ITAFs) and the Sabin point mutations likely disrupt IRES structure, the IRES RNP, or dynamic events in ribosome recruitment in ways that interfere with this process specifically in neurons [18,23–25]. …”