title: Herpes simplex virus 2 expresses a novel form of ICP34.5, a major viral neurovirulence factor, through regulated alternative splicing.
abstract: Herpes simplex virus 1 (HSV-1) and HSV-2, two closely related neurotropic human herpesviruses, achieve neurotropism through ICP34.5, a major viral neurovirulence factor. In this report, in addition to the full-length 38-kDa protein (ICP34.5α), we identified a 28-kDa novel form of ICP34.5 (ICP34.5β) in HSV-2-infected cells. ICP34.5β is translated from unspliced ICP34.5 mRNA, with the retained intron introducing a premature stop codon. Thus, ICP34.5β lacks the C-terminal conserved GADD34 domain but includes 19 additional amino acids encoded by the intron. Although a fraction of both HSV-2 ICP34.5 proteins are detected in the nucleolus, ICP34.5α is predominantly located in cytoplasm, and ICP34.5β is mainly detected more diffusely in the nucleus. ICP34.5β is unable to counteract PKR-mediated eIF2 phosphorylation but does not interfere with ICP34.5α's function in this process. Efficient expression of ICP34.5β in cell culture assays is dependent on viral infection or expression of ICP27, a multifunctional immediate-early gene. The effect of ICP27 on the ICP34.5β protein level is attributed to its selective inhibition of ICP34.5 splicing, which results in increased expression of ICP34.5β but a reduced level of ICP34.5α. The C- terminal KH3 domain but not the RNA binding domain of ICP27 is required for its specific inhibition of ICP34.5 splicing and promotion of ICP34.5β expression. Our results suggest that the expression of ICP34.5α and ICP34.5β is tightly regulated in HSV-2 and likely contributes to viral pathogenesis.
authors.affiliation: Division of Viral Products, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland, USA.
authors.forename: Shuang
authors.initials: S
authors.lastname: Tang
authors.forename: Nini
authors.initials: N
authors.lastname: Guo
authors.forename: Amita
authors.initials: A
authors.lastname: Patel
authors.forename: Philip R
authors.initials: PR
authors.lastname: Krause
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000737:chemistry; D003593:Cytoplasm / Q000737:chemistry; D018258:Herpesvirus 2, Human / Q000235:genetics* / Q000472:pathogenicity*; D006801:Humans; D014764:Viral Proteins / Q000096:biosynthesis* / Q000235:genetics; D037521:Virulence Factors / Q000096:biosynthesis* / Q000235:genetics
chemical_list: C540071:ICP34.5 protein, human herpesvirus-2; D014764:Viral Proteins; D037521:Virulence Factors