Adenovirus 5 E1A-Mediated Suppression of p53 via FUBP1

Abstract

Far-upstream element (FUSE) binding protein 1 (FUBP1) was originally identified as a regulator of the oncogene via binding to the FUSE within the promoter and activating the expression of the gene. Recent studies have identified FUBP1 as a regulator of transcription, translation, and splicing via its DNA and RNA binding activities. Here we report the identification of FUBP1 as a novel binding partner of E1A. FUBP1 binds directly to E1A via the N terminus (residues 1 to 82) and conserved region 3 (residues 139 to 204) of adenovirus 5 E1A. The depletion of FUBP1 via short interfering RNAs (siRNA) reduces virus growth and drives the upregulation of the cellular stress response by activating the expression of p53-regulated genes. During infection, FUBP1 is relocalized within the nucleus, and it is recruited to viral promoters together with E1A while at the same time being lost from the FUSE upstream of the promoter. The depletion of FUBP1 affects viral and cellular gene expression. Importantly, in FUBP1-depleted cells, p53-responsive genes are upregulated, p53 occupancy on target promoters is enhanced, and histone H3 lysine 9 is hyperacetylated. This is likely due to the loss of the FUBP1-mediated suppression of p53 DNA binding. We also observed that E1A stabilizes the FUBP1-p53 complex, preventing p53 promoter binding. Together, our results identify, for the first time, FUBP1 as a novel E1A binding protein that participates in aspects of viral replication and is involved in the E1A-mediated suppression of p53 function. Viral infection triggers innate cellular defense mechanisms that have evolved to block virus replication. To overcome this, viruses have counterevolved mechanisms that ensure that cellular defenses are either disarmed or not activated to guarantee successful replication. One of the key regulators of cellular stress is the tumor suppressor p53 that responds to a variety of cellular stress stimuli and safeguards the integrity of the genome. During infection, many viruses target the p53 pathway in order to deactivate it. Here we report that human adenovirus 5 coopts the cellular protein FUBP1 to prevent the activation of the p53 stress response pathway that would block viral replication. This finding adds to our understanding of p53 deactivation by adenovirus and highlights its importance in infection and innate immunity.

Temporal dynamics of adenovirus 5 gene expression in normal human cells

“…Expression of all genes was normalized to cellular GAPDH and was represented as percentage of the GAPDH transcript. We have previously observed that GAPDH mRNA concentration remains steady in IMR-90 cells infected at a similar MOI for up to 48 hours after infection, therefore GAPDH mRNA was an appropriate reference gene [26]. Initially, the levels of E1A mRNA fluctuated around 0.01% of GAPDH levels, with an increase in mRNA levels occurring at the 6 hour mark (Fig 1).…”

The master regulator FUBP1: its emerging role in normal cell function and malignant development

“…During stress condition, FUBP1 binds directly to the DNA binding domain of the tumor suppressor p53 to inhibit its recruitment to target promoters [70][71][72]. Consequently, FUBP1 indirectly prevents the p53 stress response pathway that would block viral replication.…”

“…FUBP1 also promotes cancer cell proliferation by the transcriptional repression of cell cycle inhibitors P21, P15 and the activation of the positive cell cycle regulator Cyclin D2 in HCC (Table 2) [8]. FUBP1 is also implicated in the inhibition of p53 tumor suppressive activity during stress condition [70][71][72]. FUBP1 prevents the DNA-binding activity of p53, interfering with the regulation of its target genes including P21.…”

MicroRNA Expression Profile of Whole Blood Is Altered in Adenovirus-Infected Pneumonia Children

“…IMR-90 cells transfected with miRNA inhibitors were infected with HAdV5 (isolated from patients) at an MOI of 10 in serum-free medium. Virus titers were determined 72 h after infection by plaque assays performed on 293T cells [ 22 , 23 ].…”