Cooperative role of PACT and ADAR1 in preventing aberrant PKR activation by self-derived double-stranded RNA

Lavanya Manjunath, Gisselle Santiago, Pedro Ortega, Ambrocio Sanchez, Sunwoo Oh, Alexander Garcia, Junyi Li, Dana Duong, Elodie Bournique, Alexis Bouin, Bert L. Semler, Dheva Setiaputra and Rémi Buisson ()
Additional contact information
Lavanya Manjunath: Irvine
Gisselle Santiago: Irvine
Pedro Ortega: Irvine
Ambrocio Sanchez: Irvine
Sunwoo Oh: Irvine
Alexander Garcia: Irvine
Junyi Li: Irvine
Dana Duong: Irvine
Elodie Bournique: Irvine
Alexis Bouin: Irvine
Bert L. Semler: Irvine
Dheva Setiaputra: Simon Fraser University
Rémi Buisson: Irvine

Nature Communications, 2025, vol. 16, issue 1, 1-18

Abstract: Abstract Double-stranded RNAs (dsRNAs) produced during viral infections are recognized by the innate immune sensor protein kinase R (PKR), triggering a host translation shutoff that inhibits viral replication and propagation. Given the harmful effects of uncontrolled PKR activation, cells must tightly regulate PKR to ensure that its activation occurs only in response to viral infections, not endogenous dsRNAs. Here, we use CRISPR-Translate, a FACS-based genome-wide CRISPR-Cas9 knockout screening method that exploits translation levels as a readout and identifies PACT as a key inhibitor of PKR during viral infection. We find that PACT-deficient cells hyperactivate PKR in response to different RNA viruses, raising the question of why cells need to limit PKR activity. Our results demonstrate that PACT cooperates with ADAR1 to suppress PKR activation from self-dsRNAs in uninfected cells. The simultaneous deletion of PACT and ADAR1 results in synthetic lethality, which can be fully rescued in PKR-deficient cells. We propose that both PACT and ADAR1 act as essential barriers against PKR, creating a threshold of tolerable levels to endogenous dsRNA in cells without activating PKR-mediated translation shutdown and cell death.

Date: 2025
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DOI: 10.1038/s41467-025-58412-2

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