Herpes Simplex Virus 1 U _L 31 and U _L 34 Gene Products Promote the Late Maturation of Viral Replication Compartments to the Nuclear Periphery

Abstract

Herpes simplex virus 1 (HSV-1) forms replication compartments (RCs), domains in which viral DNA replication, late-gene transcription, and encapsidation take place, in the host cell nucleus. The formation of these domains leads to compression and marginalization of host cell chromatin, which forms a dense layer surrounding the viral RCs and constitutes a potential barrier to viral nuclear egress or primary envelopment at the inner nuclear membrane. Surrounding the chromatin layer is the nuclear lamina, a further host cell barrier to egress. In this study, we describe an additional phase in RC maturation that involves disruption of the host chromatin and nuclear lamina so that the RC can approach the nuclear envelope. During this phase, the structure of the chromatin layer is altered so that it no longer forms a continuous layer around the RCs but instead is fragmented, forming islands between which RCs extend to reach the nuclear periphery. Coincident with these changes, the nuclear lamina components lamin A/C and lamin-associated protein 2 appear to be redistributed via a mechanism involving the U L 31 and U L 34 gene products. Viruses in which the U L 31 or U L 34 gene has been deleted are unable to undergo this phase of chromatin reorganization and lamina alterations and instead form RCs which are bounded by an intact host cell chromatin layer and nuclear lamina. We postulate that these defects in chromatin restructuring and lamina reorganization explain the previously documented growth defects of these mutant viruses.Herpes simplex virus 1 (HSV-1) is a large double-stranded DNA virus which replicates in the nucleus of infected host cells. Viral DNA replication and late gene transcription occur in replication compartments (RCs), nuclear domains which are formed when viral replication successively annexes large portions of the nucleus during the early stages of infection. During the later stages of replication, assembly of viral capsids occurs and DNA packaging takes place in RCs. Following this, capsids move to the inner nuclear membrane (INM), where primary envelopment takes place as they bud into the perinuclear space, acquiring an envelope derived from the INM. Herpesvirus particles are then thought to fuse with the outer nuclear membrane, releasing viral nucleocapsids into the host cell cytosol (17, 28). Finally, the nucleocapsid undergoes secondary envelopment and egress from the cell (24).During RC formation and annexation of space in the host cell nucleus, cellular chromatin is marginalized and compressed (18,26). This results in a layer of host cell chromatin surrounding the RC, which potentially constitutes a barrier through which viral capsids must move to reach the INM. Thus, to bud through the INM, viral nucleocapsids must move through the compacted host chromatin and the nuclear lamina. The nuclear lamina, a proteinaceous layer underlying the INM, is composed of integral INM proteins such as lamin-associated protein 2 (LAP2) and lamin B receptor, which interact with lamin proteins A, B, and C (2, ...

p32 Is a Novel Target for Viral Protein ICP34.5 of Herpes Simplex Virus Type 1 and Facilitates Viral Nuclear Egress

“…HSV-1 infection modifies the architecture of nuclear lamina to allow nuclear egress and envelopment of viral particles (6,(11)(12)(13)(14). Prior studies demonstrate that UL31 and UL34 translocate to the nuclear rim and induce conformational changes of the nuclear lamina via association with lamin A/C or indirect recruitment of PKC␣ and PKC␦ to the nuclear membrane (12).…”

“…Besides viral glycoproteins (such as gB, gK, gD, gE, and gM) (7)(8)(9)(10), several tegument proteins are reported to modulate the nuclear egress of HSV-1. For example, UL31 and UL34 are required for conformational changes of nuclear lamina in HSV-1-infected cells (11)(12)(13)(14). Of note, UL31 is thought to form a complex with UL34 and interact with lamin A/C at the nuclear rim (15,16), which disrupts the nuclear lamina by interference with lamin-lamin interactions (5).…”

Time-resolved Global and Chromatin Proteomics during Herpes Simplex Virus Type 1 (HSV-1) Infection

“…Our study thus presents a combinatorial approach that confirms the existing data that HSV-1 disrupts the nuclear envelope likely through interrupting H3K9me3-based heterochromatin and lamin association of CBX proteins. Phosphorylation of lamin proteins and associated disruption of the lamina is a conserved feature of herpesvirus infection (16,(101)(102)(103)(104)(105)(106). Phosphorylation of lamina components during infection is mediated by both viral and cellular kinases.…”

Herpes simplex virus induces extensive modification and dynamic relocalisation of the nuclear mitotic apparatus (NuMA) protein in interphase cells

“…In addition, phosphorylation of lamins and emerin in HSV-infected cells is thought to alter the nuclear membrane meshwork and facilitate capsid egress into the cytoplasm (Morris et al, 2007;Leach et al, 2007). The virally encoded UL31 and UL34 proteins, which target the inner nuclear membrane, are required for nucleocapsid envelopment, modification of nuclear structure and efficient cytoplasmic egress of capsids (Yamauchi et al, 2001;Reynolds et al, 2001;Reynolds et al, 2002;Fuchs et al, 2002;Simpson-Holley et al, 2004;Simpson-Holley et al, 2005;Klupp et al, 2007). The viral US3 protein kinase and cellular protein kinases are also important factors in modifying the nuclear structure (Muranyi et al, 2002;Simpson-Holley et al, 2004;Reynolds et al, 2004;Simpson-Holley et al, 2005;Park and Baines, 2006;Bjerke and Roller, 2006;Mou et al, 2007).…”