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PACT, a protein activator of the interferon-induced protein kinase, PKR
1Department of Molecular Biology, The Lerner Research Institute, The Cleveland Clinic Foundation, OH 44195, USA.
Abstract:
PKR, a latent protein kinase, mediates the antiviral actions of interferon. It is also involved in cellular signal transduction, apoptosis, growth regulation and differentiation. Although in virus-infected cells, viral double-stranded (ds) RNA can serve as a PKR activator, cellular activators have remained obscure. Here, we report the cloning of PACT, a cellular protein activator of PKR. PACT heterodimerized with PKR and activated it in vitro in the absence of dsRNA. In mammalian cells, overexpression of PACT caused PKR activation and, in yeast, co-expression of PACT enhanced the anti-growth effect of PKR. Thus, PACT has the hallmarks of a direct activator of PKR.
Insights
Researchers identified PACT, a cellular protein that directly activates PKR (double-stranded RNA-dependent protein kinase). This discovery sheds light on PKR
Area of Science:
- Molecular Biology
- Immunology
- Virology
Background:
- Protein kinase R (PKR) is a key mediator of interferon's antiviral effects.
- PKR also plays roles in cellular signaling, apoptosis, and growth regulation.
- While viral double-stranded RNA activates PKR, cellular activators were previously unknown.
Purpose of the Study:
- To identify and characterize cellular activators of Protein Kinase R (PKR).
Main Methods:
- Cloning of the PACT gene.
- In vitro biochemical assays to assess PACT-PKR interaction and activation.
- Overexpression studies in mammalian cells and yeast.
Main Results:
- PACT was cloned as a direct activator of PKR.
- PACT heterodimerizes with PKR, activating it independently of double-stranded RNA.
- PACT overexpression activates PKR in mammalian cells and enhances PKR's anti-growth effects in yeast.
Conclusions:
- PACT is a novel cellular activator of PKR.
- PACT represents a crucial link in PKR-mediated cellular responses.
- Understanding PACT's role may offer new avenues for antiviral and anti-cancer therapies.