WDR5 Facilitates Human Cytomegalovirus Replication by Promoting Capsid Nuclear Egress

Abstract

WD repeat-containing protein 5 (WDR5) is essential for assembling the VISA-associated complex to induce a type I interferon antiviral response to Sendai virus infection. However, the roles of WDR5 in DNA virus infections are not well described. Here, we report that human cytomegalovirus exploits WDR5 to facilitate capsid nuclear egress. Overexpression of WDR5 in fibroblasts slightly enhanced the infectious virus yield. However, WDR5 knockdown dramatically reduced infectious virus titers with only a small decrease in viral genome replication or gene expression. Further investigation of late steps of viral replication found that WDR5 knockdown significantly impaired formation of the viral nuclear egress complex and induced substantially fewer infoldings of the inner nuclear membrane. In addition, fewer capsids were associated with these infoldings, and there were fewer capsids in the cytoplasm. Restoration of WDR5 partially reversed these effects. These results suggest that WDR5 knockdown impairs the nuclear egress of capsids, which in turn decreases virus titers. These findings reveal an important role for a host factor whose function(s) is usurped by a viral pathogen to promote efficient replication. Thus, WDR5 represents an interesting regulatory mechanism and a potential antiviral target. Human cytomegalovirus (HCMV) has a large (∼235-kb) genome with over 170 open reading frames and exploits numerous cellular factors to facilitate its replication. HCMV infection increases protein levels of WD repeat-containing protein 5 (WDR5) during infection, overexpression of WDR5 enhances viral replication, and knockdown of WDR5 dramatically attenuates viral replication. Our results indicate that WDR5 promotes the nuclear egress of viral capsids, the depletion of WDR5 resulting in a significant decrease in production of infectious virions. This is the first report that WDR5 favors HCMV, a DNA virus, replication and highlights a novel target for antiviral therapy.

Human Cytomegalovirus Drives WDR5 to the Virion Assembly Compartment to Facilitate Virion Assembly

“…Measles virus recruits WDR5 into viral inclusion bodies in the cytoplasm to facilitate virus replication (46). Our previous work showed that WDR5 promotes HCMV replication through facilitating capsid nuclear egress (47). In the present study, we further demonstrate that in HCMV-infected cells WDR5 protein levels increase in the cytoplasm and that WDR5 is translocated to and accumulates in the vAC.…”

“…We further examine the virion morphogenesis by TEM in Ctl and KD cells. We previously have reported that knockdown of WDR5 dramatically decreased the number of matured virions in the vAC (47). As shown in Fig Fig 4B) both affect WDR5 accumulation in vAC, knock down WDR5 by shRNA altered formation and/or morphology of vAC ( Fig 4D).…”

“…Coverslips were collected at the indicated times post infection and fixed with 4% paraformaldehyde. Target proteins were detected by incubation with primary antibodies and appropriate secondary antibodies, as listed in Table 2, and as described previously (47). Nuclei were counterstained with DAPI (Cat.#D9542, Sigma).…”

“…To further explore whether WDR5 contributes to formation of vAC, we used a previously described pair of HELF-derived cell lines, one in which WDR5 is knocked down by shRNA (KD) and one expressing an irrelevant control shRNA (Ctl) (47). In KD cells, WDR5 knockdown altered formation and/or morphology of vAC, as determined by staining for gB.…”

RNA-Binding Motif Protein 24 (RBM24) Is Involved in Pregenomic RNA Packaging by Mediating Interaction between Hepatitis B Virus Polymerase and the Epsilon Element

“…HEK293T cells transfected with the indicated plasmids were lysed with immunoprecipitation (IP) buffer at 48 h posttransfection (hpt). Cell lysates containing 800 g total protein were incubated with protein G beads precoated with mouse anti-Flag (catalog number F1804; Sigma-Aldrich) or a nonspecific mouse IgG control antibody (catalog number I5381; Sigma), as described previously (37). Whole-cell lysates and precipitates were detected by Western blotting.…”