PKR in the cytoplasm is activated by multiple stimuli, such as cytokines (IFNs, etc), bacterial and viral infection, and DNA damage. Active PKR triggers production of IFNs and proinflammatory cytokines, apoptosis, and autophagy. In this study, Cheng et al showed that nuclear PKR activates PP2A by promoting nuclear localization of the regulatory B subunit (B55α). Activated PP2A in turn antagonizes autophosphorylation and activation of ATM, thereby inhibiting DNA damage response. P indicates phosphorylation. See Figure 4I in the article by Cheng et al beginning on page 1585.