Role and modulation of Zinc-finger antiviral protein and antiviral Regnase-1-like endonucleases

The human zinc finger antiviral protein (ZAP) is capable of inhibiting several major human pathogens, including Influenza A virus and SARS-CoV-2. ZAP specifically targets CpG dinucleotides in RNAs and might be one of the reasons why CpGs are strongly suppressed in the human genome. Successful viruses, such as HIV-1 and SARS-CoV-2, mimic human CpG suppression to partially evade the inhibitory effects of ZAP. However, especially under conditions of infection or inflammation when ZAP is expressed at high levels, it inhibits both CpG containing viral as well as cellular RNAs. Importantly, ZAP itself does not possess RNAse activity and is dependent on cofactors, such as KHNYN, to destroy viral RNAs. KHNYN is tightly regulated and inactivated by MALT-1, a cellular protease representing an important target in cancer immunotherapies. Although some progress has been made, the identity of ZAP cofactors as well as their mechanism(s) of action and therapeutic potential are poorly understood. This proposal aims to combine the expertise of the applicant (mechanistic studies of ZAP and RNA-targeting factors) and the host (respiratory viruses and antiviral drug development) to define how ZAP-dependent and independent antiviral endonucleases restrict major respiratory viral pathogens. In addition, it will be examined whether MALT-1 inhibitors that are currently in clinical trials against cancers allow to enhance and maintain the antiviral activity of ZAP and its cofactors thus offering prospects for the treatment of respiratory infections. Finally, potential side-effects on cellular RNAs and their impact on immune signalling, cell activation and infection outcome will be determined. The project will combine innovative CRISPR/Cas9 genome editing, in vitro virus infection platforms, novel functional assays and state-of-the-art deep sequencing technologies to significantly advance the knowledge on antiviral RNAses and to clarify whether they can be strengthened for antiviral therapy.