E2F/Rb Family Proteins Mediate Interferon Induced Repression of Adenovirus Immediate Early Transcription to Promote Persistent Viral Infection.

Yueting Zheng,Patrick Hearing,Thomas Stamminger,Michael J Imperiale

doi:10.1371/journal.ppat.1005415

Yueting Zheng, Patrick Hearing + Show 2 more

Open Access

https://doi.org/10.1371/journal.ppat.1005415

Copy DOI

Abstract

Interferons (IFNs) are cytokines that have pleiotropic effects and play important roles in innate and adaptive immunity. IFNs have broad antiviral properties and function by different mechanisms. IFNs fail to inhibit wild-type Adenovirus (Ad) replication in established cancer cell lines. In this study, we analyzed the effects of IFNs on Ad replication in normal human cells. Our data demonstrate that both IFNα and IFNγ blocked wild-type Ad5 replication in primary human bronchial epithelial cells (NHBEC) and TERT-immortalized normal human diploid fibroblasts (HDF-TERT). IFNs inhibited the replication of divergent adenoviruses. The inhibition of Ad5 replication by IFNα and IFNγ is the consequence of repression of transcription of the E1A immediate early gene product. Both IFNα and IFNγ impede the association of the transactivator GABP with the E1A enhancer region during the early phase of infection. The repression of E1A expression by IFNs requires a conserved E2F binding site in the E1A enhancer, and IFNs increased the enrichment of the E2F-associated pocket proteins, Rb and p107, at the E1A enhancer in vivo. PD0332991 (Pabociclib), a specific CDK4/6 inhibitor, dephosphoryles pocket proteins to promote their interaction with E2Fs and inhibited wild-type Ad5 replication dependent on the conserved E2F binding site. Consistent with this result, expression of the small E1A oncoprotein, which abrogates E2F/pocket protein interactions, rescued Ad replication in the presence of IFNα or IFNγ. Finally, we established a persistent Ad infection model in vitro and demonstrated that IFNγ suppresses productive Ad replication in a manner dependent on the E2F binding site in the E1A enhancer. This is the first study that probes the molecular basis of persistent adenovirus infection and reveals a novel mechanism by which adenoviruses utilize IFN signaling to suppress lytic virus replication and to promote persistent infection.

Highlights

Interferons (IFNs) are widely expressed cytokines that have pleiotropic effects on cells
We demonstrate that type I (IFNα) and type II (IFNγ) IFNs inhibit the replication of divergent adenoviruses via an evolutionally conserved E2F binding site
By comparing the properties of wild type and E2F site mutant viruses, we show that the IFN–E2F/Rb axis is critical for restriction of adenovirus replication to promote persistent viral infection

Summary

Introduction

Interferons (IFNs) are widely expressed cytokines that have pleiotropic effects on cells. IFNs play important roles in both innate and adaptive immunity [1,2]. There are three types of IFNs: I, II and III. Type I IFNs (α, β, ε, κ and ω) are produced by multiple cell types following the activation of pathogen pattern recognitions receptors and function in both an autocrine and paracrine manner. Type II IFN (γ) is produced by T cells and natural killer cells, as well as other cells of the immune system. Type III IFNs (λs) play an important role in mucosal cell immunity. All three types of IFNs bind to cell surface receptors that activate Janus kinases to phosphoryate STAT (Signal Tranducer of Activated Transcription) proteins [1,2]. STAT proteins homo- and heterodimerize and induce the expression of numerous IFN-stimulated genes (ISGs) that have antimicrobial properties [3]. IFNs have broad antiviral properties and function by different mechanisms

Methods

Results

Discussion

Conclusion