title: The Herpes Simplex Virus Protein pUL31 Escorts Nucleocapsids to Sites of Nuclear Egress, a Process Coordinated by Its N-Terminal Domain.
abstract: Progeny capsids of herpesviruses leave the nucleus by budding through the nuclear envelope. Two viral proteins, the membrane protein pUL34 and the nucleo-phosphoprotein pUL31 form the nuclear egress complex that is required for capsid egress out of the nucleus. All pUL31 orthologs are composed of a diverse N-terminal domain with 1 to 3 basic patches and a conserved C-terminal domain. To decipher the functions of the N-terminal domain, we have generated several Herpes simplex virus mutants and show here that the N-terminal domain of pUL31 is essential with basic patches being critical for viral propagation. pUL31 and pUL34 entered the nucleus independently of each other via separate routes and the N-terminal domain of pUL31 was required to prevent their premature interaction in the cytoplasm. Unexpectedly, a classical bipartite nuclear localization signal embedded in this domain was not required for nuclear import of pUL31. In the nucleus, pUL31 associated with the nuclear envelope and newly formed capsids. Viral mutants lacking the N-terminal domain or with its basic patches neutralized still associated with nucleocapsids but were unable to translocate them to the nuclear envelope. Replacing the authentic basic patches with a novel artificial one resulted in HSV1(17+)Lox-UL31-hbpmp1mp2, that was viable but delayed in nuclear egress and compromised in viral production. Thus, while the C-terminal domain of pUL31 is sufficient for the interaction with nucleocapsids, the N-terminal domain was essential for capsid translocation to sites of nuclear egress and a coordinated interaction with pUL34. Our data indicate an orchestrated sequence of events with pUL31 binding to nucleocapsids and escorting them to the inner nuclear envelope. We propose a common mechanism for herpesviral nuclear egress: pUL31 is required for intranuclear translocation of nucleocapsids and subsequent interaction with pUL34 thereby coupling capsid maturation with primary envelopment.
authors.affiliation: Institute for Interfacial Engineering and Plasma Technology (IGVP), University of Stuttgart, Stuttgart, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Funk
authors.affiliation: Max von Pettenkofer-Institut, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Ott
authors.affiliation: Max von Pettenkofer-Institut, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Raschbichler
authors.affiliation: Institute of Virology, Hannover Medical School, Hannover, Germany.
authors.forename: Claus-Henning
authors.initials: CH
authors.lastname: Nagel
authors.affiliation: Institute of Virology, Hannover Medical School, Hannover, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Binz
authors.affiliation: Institute of Virology, Hannover Medical School, Hannover, Germany.
authors.forename: Beate
authors.initials: B
authors.lastname: Sodeik
authors.affiliation: Institute of Cell Biology, Hannover Medical School, Hannover, Germany.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Bauerfeind
authors.affiliation: Institute for Interfacial Engineering and Plasma Technology (IGVP), University of Stuttgart, Stuttgart, Germany; Max von Pettenkofer-Institut, Ludwig-Maximilians-University Munich, Munich, Germany; Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB), Stuttgart, Germany.
authors.forename: Susanne M
authors.initials: SM
authors.lastname: Bailer
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000818:Animals; D002522:Chlorocebus aethiops; D006367:HeLa Cells; D018259:Herpesvirus 1, Human / Q000502:physiology*; D006801:Humans; D008856:Microscopy, Fluorescence; D016297:Mutagenesis, Site-Directed; D019590:Nucleocapsid Proteins / Q000378:metabolism*; D014709:Vero Cells; D019065:Virus Assembly / Q000502:physiology*
chemical_list: D019590:Nucleocapsid Proteins