Reovirus-Induced Alteration in Expression of Apoptosis and DNA Repair Genes with Potential Roles in Viral Pathogenesis

Abstract

Reoviruses are a leading model for understanding cellular mechanisms of virus-induced apoptosis. Reoviruses induce apoptosis in multiple cell lines in vitro, and apoptosis plays a key role in virus-induced tissue injury of the heart and brain in vivo. The activation of transcription factors NF-B and c-Jun are key events in reovirus-induced apoptosis, indicating that new gene expression is critical to this process. We used highdensity oligonucleotide microarrays to analyze cellular transcriptional alterations in HEK293 cells after infection with reovirus strain T3A (i.e., apoptosis inducing) compared to infection with reovirus strain T1L (i.e., minimally apoptosis inducing) and uninfected cells. These strains also differ dramatically in their potential to induce apoptotic injury in hearts of infected mice in vivo-T3A is myocarditic, whereas T1L is not. Using high-throughput microarray analysis of over 12,000 genes, we identified differential expression of a defined subset of genes involved in apoptosis and DNA repair after reovirus infection. This provides the first comparative analysis of altered gene expression after infection with viruses of differing apoptotic phenotypes and provides insight into pathogenic mechanisms of virus-induced disease.

Mechanisms of Apoptosis During Reovirus Infection

“…Changes in the expression of genes encoding proteins known to be involved in DNA repair and cell cycle regulation were also identified in this study and may also affect virus-induced pathogenesis (DeBiasi et al 2003).…”

“…This gene was found by polymerase chain reaction (PCR) analysis to be upregulated at the transcriptional level in reovirus-infected HEK293 cells and at the translational level in the hearts of reovirus-infected baby mice (DeBiasi et al 2003). The SMN protein has been shown to interact with Bcl-2, conferring a synergistic protective effect against Bax-induced or Fas-mediated apoptosis that has been shown to underlie the pathogenesis of spinal muscular atrophy (Sato et al 2000;Iwahashi et al 1997).…”

“…The early activation of calpain after reovirus infection makes this an attractive candidate for reovirus-induced activation of NF-κB. In addition, reovirus induces the up-regulation of the proapoptotic protein par-4 (DeBiasi et al 2003), which can inhibit the phosphorylation and degradation of IκB, thereby preventing NF-κB activation (Camandola and Mattson 2000;Diaz-Meco et al 1999). This results in the downmodulation of Bcl-2 and can result in sensitization of cells to TNF-and FasL-induced apoptosis (Diaz-Meco et al 1999).…”

“…High-density oligonucleotide microarrays used to perform a global analysis of virus-induced cellular gene expression after reovirus infection of HEK293 cells (DeBiasi et al 2003;Poggioli et al 2002) showed that the expression of 24 genes related to apoptosis were altered in cells infected with the apoptosis-inducing reovirus strain T3A (Table 1). These genes encode proteins with potential roles in DR, endoplasmic reticulum stress, and mitochondrial apoptotic signaling and cysteine proteases (caspases and calpains) (DeBiasi et al 2003). Only five of these genes were also differentially expressed after T1L (weakly apoptotic) infection, emphasizing their potential importance in reovirus-induced apoptosis.…”

Down-regulation of cFLIP following reovirus infection sensitizes human ovarian cancer cells to TRAIL-induced apoptosis

“…Enhanced apoptosis in the TRAIL-treated Jurkat cells was brought about by enforced cleavage of cFLIP together with increased activation of the initiator caspases 8 and 10. Microarray analysis indicates that par-4 expression is increased in HEK293 cells following reovirus infection [69] representing a potential mechanism for the down-regulation of cFLIP in OVCAR3 cells.…”