PARP11

PARP11 (ARTD11) is a nuclear envelope-localized mono-ADP-ribosyltransferase that links protein and RNA ADP-ribosylation to antiviral immunity, anti-tumor immune regulation, and spermatid development (PMID:30988430, PMID:25673562, PMID:36018800). It is targeted to the nuclear envelope through its N-terminal WWE domain (residues Y77, Q86, R95) and the presence of its catalytic domain, where it co-localizes with the nucleoporin NUP153; this localization does not require catalytic activity per se, yet pharmacologic inhibition of its MARylation activity with the selective inhibitor ITK7 causes PARP11 to dissociate from the nuclear envelope (PMID:25673562, PMID:30344052). Enzymatically, PARP11 mono-ADP-ribosylates the E3 ubiquitin ligase β-TrCP to promote IFNAR1 ubiquitination and degradation, dampening type I IFN signalling and facilitating viral immune evasion (PMID:30988430). Beyond protein substrates, PARP11 ADP-ribosylates phosphorylated RNA ends in vitro and in human cells, a reversible modification removed by hydrolases such as TARG1, PARG, and ARH3; ADPr-capped mRNA is protected from XRN1-mediated degradation but is not translated (PMID:31216043, PMID:36018800). In the tumor microenvironment, immunosuppressive factors including adenosine and prostaglandin E2 induce PARP11 in intratumoral CD8+ cytotoxic T cells and regulatory T cells, where it drives IFNAR1 downregulation and immunosuppression; genetic ablation or ITK7 inhibition restores IFNAR1, reinvigorates anti-tumor immunity, and suppresses tumor growth in an IFNAR1-dependent manner (PMID:35637402, PMID:39019005). PARP11 also restricts viral infection through enzymatic-activity-independent routes, cooperating with PARP12 to degrade Zika virus NS1 and NS3 proteins (PMID:34187568). In male germ cells, PARP11 is required for spermatid nuclear shaping, with its loss causing nuclear envelope structural defects, chromatin detachment, and male infertility (PMID:25673562).

1. 2015 High

   Established where PARP11 acts and what targets it there, defining the nuclear envelope as its functional site and its requirement for sperm nuclear architecture.

   Evidence Knockout mouse, WWE-domain mutagenesis, and NUP153 colocalization imaging

   PMID:25673562

   Open questions at the time

   • Molecular mechanism connecting nuclear envelope localization to chromatin attachment unresolved
   • Substrates at the nuclear envelope not identified in this study
2. 2015 Medium

   Defined the chemistry of PARP11 auto-modification, showing it auto-ADP-ribosylates acidic residues via a distinctive C1' to C2' ribose transfer.

   Evidence Clickable aminooxy alkyne chemical probe and click chemistry in cells

   PMID:25978521

   Open questions at the time

   • Functional consequence of auto-modification unknown
   • Single chemical-probe method
3. 2016 Medium

   Identified PARP11's protein MARylome, revealing nuclear pore complex proteins as isoform-specific targets and that targeting requires both regulatory and catalytic domains.

   Evidence Engineered orthogonal NAD+ analog, in vitro MARylation, mass spectrometry

   PMID:26774478

   Open questions at the time

   • In vitro targets not validated in cells
   • Functional impact of nucleoporin MARylation unestablished
4. 2018 High

   Provided a selective chemical tool (ITK7) and showed that PARP11 catalytic activity governs its own nuclear envelope retention.

   Evidence Structure-guided inhibitor design, in vitro inhibition assay, live-cell imaging

   PMID:30344052

   Open questions at the time

   • Endogenous substrate driving localization not identified
   • Reconciliation with the earlier finding that catalysis is not required for NUP153 colocalization unaddressed
5. 2019 High

   Connected PARP11 enzymatic activity to a defined physiological pathway by identifying β-TrCP as a substrate that channels IFNAR1 degradation and viral immune evasion.

   Evidence ADP-ribosylation assays, reciprocal Co-IP, loss/gain-of-function, in vivo mouse viral infection

   PMID:30988430

   Open questions at the time

   • Modified residues on β-TrCP not mapped
   • How β-TrCP MARylation mechanistically enhances IFNAR1 ubiquitination unclear
6. 2019 High

   Expanded the substrate class of PARP11 from proteins to RNA, showing it mono-ADP-ribosylates phosphorylated RNA ends reversibly.

   Evidence In vitro ADP-ribosylation of purified RNA substrates and hydrolase reversal assays

   PMID:31216043

   Open questions at the time

   • In vitro only at this stage
   • Biological RNA targets not defined
7. 2021 Medium

   Showed PARP11 restricts viral infection through an enzymatic-activity-independent route, cooperating with PARP12 to degrade Zika virus proteins.

   Evidence Multiple KO cell lines, Co-IP, western blot, immunofluorescence in A549 and HEK293T

   PMID:34187568

   Open questions at the time

   • Mechanism of PARP11-PARP12 cooperation undefined
   • Single lab, no in vivo confirmation
8. 2022 High

   Demonstrated RNA ADP-ribosylation by PARP11 occurs in human cells with functional consequences, protecting capped mRNA from XRN1 degradation while blocking translation.

   Evidence Cellular RNA ADP-ribosylation assays with PARP KO/overexpression and functional degradation/translation assays

   PMID:36018800

   Open questions at the time

   • Endogenous mRNA targets and physiological scope unknown
   • Link to PARP11's nuclear envelope localization not established
9. 2022 High

   Placed PARP11 at the center of tumor immunosuppression in cytotoxic T cells, showing TME factors induce it to downregulate IFNAR1 and that its ablation restores anti-tumor immunity.

   Evidence Genetic KO and ITK7 inhibition in tumor-bearing mice, CAR T engineering, in vivo tumor models

   PMID:35637402

   Open questions at the time

   • Whether β-TrCP MARylation mediates CTL IFNAR1 loss not directly tested here
   • Direct enzymatic substrate in CTLs not pinpointed
10. 2022 Medium

    Identified ACTRT1 as a nuclear envelope partner of PARP11 that anchors developing acrosomes to the sperm nucleus.

    Evidence Co-IP, Actrt1-KO mouse, immunofluorescence

    PMID:35616329

    Open questions at the time

    • Direct vs indirect PARP11-ACTRT1 interaction not resolved
    • Role of PARP11 catalysis in acrosome anchoring untested
11. 2024 High

    Extended PARP11's immunoregulatory role to regulatory T cells, showing TME-induced PARP11 sustains TI-Treg immunosuppression and that its inhibition reinvigorates anti-tumor responses.

    Evidence PARP11 KO and ITK7 inhibition in tumor-bearing mice, immune functional assays, ICB and CAR T combinations

    PMID:39019005

    Open questions at the time

    • Molecular substrate in Tregs not identified
    • Relationship to IFNAR1 axis in Tregs vs CTLs not fully delineated
12. 2024 Medium

    Showed PARP11 antiviral restriction extends across species and pathways, regulating nuclear export factors and autophagy/mTOR during pseudorabies virus infection.

    Evidence CRISPR/Cas9 KO PK-15 cells, RT-qPCR, TCID50, RNA-seq, western blot

    PMID:39445214

    Open questions at the time

    • Direct PARP11 substrate driving NXF1/CRM1 and autophagy changes unknown
    • Whether effects require catalytic activity untested

• It remains unresolved how PARP11's catalytic and enzymatic-activity-independent functions are integrated, and which endogenous substrates mediate its distinct roles in immunity, RNA metabolism, and spermatogenesis.
• No unified model linking nuclear envelope localization to its diverse substrates
• Physiological RNA substrates undefined
• Substrate(s) underlying tumor-immune phenotypes not pinpointed in vivo