Abstract
The p53 transcription factor plays a key role both in cancer and in the cell-intrinsic response to infections. The ORFEOME project hypothesized that novel p53-virus interactions reside in hitherto uncharacterized, unknown, or hypothetical open reading frames (orfs) of human viruses. Hence, 172 orfs of unknown function from the emerging viruses SARS-Coronavirus, MERS-Coronavirus, influenza, Ebola, Zika (ZIKV), Chikungunya and Kaposi Sarcoma-associated herpesvirus (KSHV) were de novo synthesized, validated and tested in a functional screen of p53 signaling. This screen revealed novel mechanisms of p53 virus interactions and two viral proteins KSHV orf10 and ZIKV NS2A binding to p53. Originally identified as the target of small DNA tumor viruses, these experiments reinforce the notion that all viruses, including RNA viruses, interfere with p53 functions. These results validate this resource for analogous systems biology approaches to identify functional properties of uncharacterized viral proteins, long non-coding RNAs and micro RNAs.
Highlights
The p53 tumor suppressor protein is a transcription factor
The ORFEOME project was based on the hypothesis that every virus, regardless of its molecular makeup and biology should encode functions that intersect the p53 signaling network, since p53 guards the cell from genomic insults, of which depositing a foreign, viral nucleic acid is one
The result of the ORFEOME screen of proteins without any known function, of predicted open reading frames and of suspected non-coding RNAs is the identification of two viral proteins that interact with p53
Summary
The p53 tumor suppressor protein is a transcription factor. It has been called the “guardian of the genome” and it plays major roles in the maintenance of genomic stability, DNA repair, cell cycle arrest, apoptosis, and cell differentiation (reviewed in [1]). P53 protein expression is low and tightly regulated by its interactions with E3 ubiquitin ligases, primarily mouse double minute 2 and its human homolog, human double minute 2 (HDM2). These interactions lead to p53 ubiquitination and degradation via the proteasome pathway. Upon induction of the DNA damage response (DDR) pathway, the DNA damage-sensing kinases, ataxia telangiectasia mutated kinase (ATM), Rad3-Related kinase (ATR), and DNA protein kinase phosphorylate downstream proteins, including HDM2 and p53 This phosphorylation event disrupts the HDM2-p53 interaction, resulting in p53 stabilization, phosphorylation, accumulation, cytoplasmic to nuclear re-localization, and subsequent transcription of p53 target genes, such as p21 (Fig 1A). Any one of these steps poses a target for viral proteins to interrupt p53 signaling and premature apoptosis of the infected cell
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