ZCCHC3

ZCCHC3 is a nucleic-acid-binding co-sensor that potentiates multiple arms of innate antiviral immunity by recognizing both viral RNA and DNA (PMID:30193849, PMID:30135424). In the RNA-sensing pathway it directly binds dsRNA, enhances dsRNA recognition by RIG-I and MDA5, and recruits the E3 ligase TRIM25 to drive K63-linked polyubiquitination and activation of these receptors (PMID:30193849); in the DNA-sensing pathway it binds dsDNA and enhances cGAS engagement of DNA, with ZCCHC3-deficient mice showing increased susceptibility to HSV-1 and vaccinia virus (PMID:30135424). It also promotes recruitment of the adaptor TRIF to TLR3 to support TLR3-restricted type I interferon induction (PMID:32133501). The unifying biophysical mechanism is liquid-phase condensation: upon RNA or DNA binding ZCCHC3 forms condensates that enrich and activate RLRs, facilitate RLR engagement of MAVS and assembly of active MAVS filaments, and concentrate DNA, cGAS, ATP and GTP to enhance cGAS signaling, with condensation-defective mutants losing activity in both pathways (PMID:39983719). Beyond pathogen sensing, ZCCHC3 acts as a restriction factor: it binds LINE-1 RNA and the ORF1p ribonucleoprotein in stress granules and routes LINE-1 RNA to degradation via the RNA exosome in a zinc-finger-dependent manner (PMID:37405998, PMID:36274734), and it suppresses HIV-1 through zinc-finger-mediated binding of Gag nucleocapsid that blocks genome packaging together with LTR binding that sequesters the viral genome to P-bodies (PMID:38384847).

1. 2018 High

   Established ZCCHC3 as an RLR co-receptor, answering how RIG-I/MDA5 dsRNA sensing is enhanced and linked to ubiquitin-dependent activation.

   Evidence Co-IP, RNA binding assays, and KO mouse viral challenge with downstream gene induction readouts

   PMID:30193849

   Open questions at the time

   • Did not resolve the structural basis of dsRNA binding
   • Stoichiometry of the ZCCHC3–RIG-I/MDA5–TRIM25 assembly not defined
2. 2018 High

   Extended ZCCHC3 function to the DNA-sensing axis, showing it is also a cGAS co-sensor required for full antiviral defense against DNA viruses.

   Evidence dsDNA binding assays, Co-IP, and KO mice challenged with HSV-1 and vaccinia virus

   PMID:30135424

   Open questions at the time

   • How one protein discriminates or simultaneously serves DNA and RNA pathways not addressed
   • Direct effect on cGAMP output not quantified at this stage
3. 2020 High

   Showed ZCCHC3 also operates upstream in TLR3 signaling by promoting TRIF adaptor recruitment, broadening its role beyond cytosolic sensors.

   Evidence Co-IP, overexpression, and KO mice with poly(I:C)-induced inflammatory death, with TLR4 as negative control

   PMID:32133501

   Open questions at the time

   • Direct ZCCHC3–TLR3 or ZCCHC3–TRIF binding interface not mapped
   • Relationship between endosomal TLR3 role and cytosolic RLR role unclear
4. 2022 Medium

   Identified ZCCHC3 as a LINE-1 restriction factor acting post-transcriptionally, defining a non-immune-signaling activity.

   Evidence Retrotransposition reporter assays, zinc-finger mutagenesis, RNA co-IP, and RT-qPCR of LINE-1 RNA

   PMID:36274734

   Open questions at the time

   • Single lab
   • Direct ribonuclease activity vs. recruitment of a nuclease not distinguished
5. 2023 Medium

   Placed LINE-1 restriction in stress granules and connected it to the RNA exosome, providing a degradation route for ORF1p-bound RNA.

   Evidence Retrotransposition reporters, Co-IP, stress-granule immunofluorescence, and velocity gradient centrifugation

   PMID:37405998

   Open questions at the time

   • Single lab
   • Whether ZCCHC3 directly bridges ORF1p RNP to the exosome or acts via MOV10/ZAP unresolved
6. 2024 Medium

   Defined a dual zinc-finger/LTR-binding mechanism by which ZCCHC3 restricts HIV-1, linking nucleic-acid binding to both packaging block and P-body sequestration.

   Evidence Co-IP of ZCCHC3–GagNC, P-body imaging, virion RNA quantification, and domain mutagenesis

   PMID:38384847

   Open questions at the time

   • Single lab
   • Generality across other retroviruses not tested directly
7. 2025 High

   Unified the RNA and DNA co-sensing functions under a single biophysical mechanism—nucleic-acid-induced condensation that concentrates and activates sensors and adaptors.

   Evidence Liquid-phase condensation assays, high-resolution structural analysis of MAVS filaments, mutagenesis, and in vitro reconstitution in human cells

   PMID:39983719

   Open questions at the time

   • Whether condensation is also required for the TLR3, LINE-1, and HIV-1 functions not tested
   • In vivo relevance of condensation thresholds unknown
8. 2025 Medium

   Extended antiviral activity to a coronavirus by showing ZCCHC3 drives proteasomal degradation of PEDV nucleocapsid.

   Evidence Co-IP, co-localization, knockdown/overexpression viral titer assays, and proteasome inhibitor experiments

   PMID:40068467

   Open questions at the time

   • Single lab
   • Whether ZCCHC3 itself has protease/ligase activity or recruits one is not biochemically resolved

• Whether the condensation mechanism, zinc-finger nucleic-acid binding, and protein-degradation activities are mechanistically linked across the antiviral, retrotransposon-restriction, and reported cancer/senescence contexts remains open.
• No structural model of ZCCHC3 itself
• Reported TNBC/NCAPH and senescence roles rest on low-confidence single-lab phenotypes without direct biochemical mechanism