Baculovirus F-Box Protein LEF-7 Modifies the Host DNA Damage Response To Enhance Virus Multiplication

Abstract

The DNA damage response (DDR) of a host organism represents an effective antiviral defense that is frequently manipulated and exploited by viruses to promote multiplication. We report here that the large DNA baculoviruses, which require host DDR activation for optimal replication, encode a conserved replication factor, LEF-7, that manipulates the DDR via a novel mechanism. LEF-7 suppresses DDR-induced accumulation of phosphorylated host histone variant H2AX (␥-H2AX), a critical regulator of the DDR. LEF-7 was necessary and sufficient to block ␥-H2AX accumulation caused by baculovirus infection or DNA damage induced by means of pharmacological agents. Deletion of LEF-7 from the baculovirus genome allowed ␥-H2AX accumulation during virus DNA synthesis and impaired both very late viral gene expression and production of infectious progeny. Thus, LEF-7 is essential for efficient baculovirus replication. We determined that LEF-7 is a nuclear F-box protein that interacts with host S-phase kinase-associated protein 1 (SKP1), suggesting that LEF-7 acts as a substrate recognition component of SKP1/Cullin/F-box (SCF) complexes for targeted protein polyubiquitination. Site-directed mutagenesis demonstrated that LEF-7's N-terminal F-box is necessary for ␥-H2AX repression and Autographa californica multiple nucleopolyhedrovirus (AcMNPV) replication events. We concluded that LEF-7 expedites virus replication most likely by selective manipulation of one or more host factors regulating the DDR, including ␥-H2AX. Thus, our findings indicate that baculoviruses utilize a unique strategy among viruses for hijacking the host DDR by using a newly recognized F-box protein.

Orientia tsutsugamushi Strain Ikeda Ankyrin Repeat-Containing Proteins Recruit SCF1 Ubiquitin Ligase Machinery via Poxvirus-Like F-Box Motifs

“…numerous viruses (particularly poxviruses) (39,42,(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59); various plant bacterial pathogens (22,60,61); and several intracellular bacteria that infect mammals, such as Legionella pneumophila (20-22, 31, 34, 35), Coxiella burnetii (22,32,37), Salmonella enterica serovar Typhimurium (36), and Chlamydia spp. (22,32,33).…”

Insect Inhibitor-of-Apoptosis (IAP) Proteins Are Negatively Regulated by Signal-Induced N-Terminal Degrons Absent within Viral IAP Proteins

“…For transfections, monolayers were overlaid with medium containing purified plasmid DNA mixed with cationic liposomes consisting of N- [1-(2,3 dioleoyloxy) propyl]-N,N,N-trimethylammonium methyl sulfate-L-␣-phosphatidylethanolamine, dioleoyl (C 18:1 [cis]-9; DOTAP-DOPE) as described previously (32). AcMNPV late gene expression assays used a lacZ reporter under the control of the polyhedrin promoter of v⌬p35/lacZ as described previously (19,20,33). Intracellular ␤-galactosidase was measured 48 h after infection of plasmid-transfected SF21 cells by using a Galacto-Light Plus ␤-galactosidase chemiluminescent reporter assay (Tropix) and is reported as the average activities Ϯ the standard deviations obtained from triplicate infections.…”

Baculoviruses and nucleosome management

“…Baculoviruses also induce the DDR during genome replication and processing; and, as it does for the polyomaviruses and papillomaviruses, this response contributes to baculovirus production (Huang et al, 2011;Mitchell and Friesen, 2012;Mitchell et al, 2013). It should be noted that the DDR includes recruitment of chromatin-modifying complexes, which is favorable for viral DNA replication and processing (Morrison and Shen, 2009).…”