Affinage

RNF121

E3 ubiquitin ligase RNF121 · UniProt Q9H920

Length
327 aa
Mass
37.9 kDa
Annotated
2026-06-10
24 papers in source corpus 11 papers cited in narrative 11 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/6 claims corpus-supported (83%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

RNF121 is a RING-domain E3 ubiquitin ligase anchored in the secretory pathway, residing in the ER and cis-Golgi where it governs the maturation, surface delivery, and degradation of membrane and signaling proteins (PMID:20357004, PMID:25691753, PMID:26602861, PMID:39402275). Its catalytic RING domain drives ubiquitin-mediated proteasomal turnover of substrates that traverse or assemble in the early secretory pathway, including ER-associated degradation of beta-integrin PAT-3 in C. elegans (PMID:20357004), ER quality control of newly synthesized VEGFR-2 to restrict its glycosylation maturation and cell-surface expression and thereby limit endothelial proliferation and angiogenesis (PMID:26602861), and bidirectional control of voltage-gated sodium channels, routing them to proteasomal degradation or, with auxiliary NaVβ subunits, to the membrane (PMID:25691753). RNF121 also positively regulates NF-κB signaling, acting downstream of multiple innate-immune and stress stimuli at the level of IκBα proteasomal degradation (PMID:25388546), and supplies the K63-linked polyubiquitination of SARS-CoV-2 ORF7a needed for its engagement of TAK1 and NEMO (PMID:35856559). Beyond canonical degradative substrates, RNF121 directly binds and stabilizes the MYCN oncoprotein through Golgi-localized domains to support MYCN-amplified neuroblastoma tumorigenesis (PMID:39402275), and ubiquitinates CRTC1 to target it for degradation, a fate blocked by HIPK2-dependent Ser36 phosphorylation (PMID:40537816). Its localization and stability depend on transmembrane determinants, with a TM4 point mutation (M158R) abolishing Golgi targeting (PMID:39402275). RNF121 is genetically required for transcription from AAV capsid-associated genomes via a VCP/p97- and DNA-damage-response-linked axis (PMID:31386698), and is visualized as an associated factor at the back of the GPI transamidase complex (PMID:35165458).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2010 High

    Established RNF121 as an ER-anchored E3 ligase that routes a membrane substrate to ERAD, defining its core biochemical activity and secretory-pathway location.

    Evidence C. elegans genetics, RNAi, GFP reporter quantification, and epistasis placing RNF-121 downstream of PERK on beta-integrin PAT-3

    PMID:20357004

    Open questions at the time
    • Direct ubiquitin transfer to PAT-3 not reconstituted in vitro
    • Human substrate repertoire not addressed
    • Linkage type and degron recognition unresolved
  2. 2012 Medium

    Placed rnf-121 in a redundant E3-ligase network controlling cell migration, broadening its role beyond single-substrate degradation to developmental morphogenesis.

    Evidence C. elegans genetic epistasis with rnf-5 and ccdc-55 using deletion alleles and RNAi scoring distal tip cell migration

    PMID:22285439

    Open questions at the time
    • Functional redundancy obscures direct substrate assignment
    • Mechanism of migration termination not biochemically defined
    • Human relevance untested
  3. 2014 Medium

    Connected human RNF121 to NF-κB signaling and apoptosis suppression, showing its RING activity is required at the IκBα degradation step rather than at IKK or RIP1.

    Evidence siRNA screen of transmembrane E3 ligases, NF-κB luciferase reporters, IκBα degradation and IKK/RIP1 assays, Co-IP, RING mutants, and caspase-3/PARP apoptosis assays

    PMID:24928685 PMID:25388546

    Open questions at the time
    • RNF121 does not directly ubiquitinate IκBα, leaving the relevant substrate unidentified
    • How a Golgi-resident ligase influences cytosolic IκBα turnover is unexplained
    • Apoptosis substrate(s) unknown
  4. 2015 High

    Identified physiological vertebrate substrates (VEGFR-2 and NaV channels) and demonstrated that RNF121 can both degrade and, with cofactors, promote surface delivery of clients, establishing dual trafficking control.

    Evidence Zebrafish alligator mutant forward genetics with NaV degradation/localization assays, plus endothelial Co-IP, ubiquitination, surface-expression flow cytometry, and angiogenesis assays for VEGFR-2 with RING mutants

    PMID:25691753 PMID:26602861

    Open questions at the time
    • Molecular basis of the degradation-versus-delivery switch unresolved
    • Direct ubiquitin-chain topology on NaV/VEGFR-2 not defined
    • Cofactor requirements for membrane routing incompletely mapped
  5. 2019 High

    Revealed a non-degradative requirement for RNF121 in sustaining transcription from AAV genomes via a VCP/p97 and DNA-damage-response axis, indicating roles beyond classical substrate turnover.

    Evidence CRISPR KO with RNA Pol II ChIP, mRNA half-life, VCP/proteasome inhibitor rescue, transcriptomics/proteomics, and RING-mutant rescue

    PMID:31386698

    Open questions at the time
    • The relevant ubiquitination substrate linking RNF121 to transcriptional licensing is unidentified
    • How a Golgi/ER ligase affects nuclear AAV transcription is mechanistically unclear
    • VCP and DNAPK-Cs connection only correlative
  6. 2022 Medium

    Extended RNF121 function to viral immune modulation and revealed a stable structural association with the GPI transamidase complex.

    Evidence siRNA knockdown with K63-ubiquitination and ORF7a Co-IP/NF-κB reporter assays; separate single-particle cryo-EM at 3.1 Å of the GPIT complex

    PMID:35165458 PMID:35856559

    Open questions at the time
    • Whether RNF121 directly ubiquitinates ORF7a versus an intermediate is unresolved
    • GPIT quality-control role is interpretive and not validated by mutagenesis
    • Functional consequence of GPIT association undefined
  7. 2024 High

    Showed RNF121 stabilizes rather than degrades the MYCN oncoprotein through direct binding via Golgi-localizing transmembrane determinants, linking it causally to neuroblastoma tumorigenesis.

    Evidence ENU mutagenesis and TH-MYCN transgenic mouse model with Co-IP, MYCN stability assays, helix-5 deletion and M158R domain mutants, and hemizygous deletion in vivo

    PMID:39402275

    Open questions at the time
    • Mechanism by which a ligase stabilizes MYCN (e.g., shielding from another E3) is undefined
    • Whether stabilization requires catalytic activity is unclear
    • Subcellular site of the RNF121–MYCN interaction not pinpointed
  8. 2025 Medium

    Defined a phosphorylation-gated degradation circuit in which RNF121 ubiquitinates CRTC1 unless HIPK2 phosphorylates CRTC1 at Ser36, integrating RNF121 into hormone-regulated transcription.

    Evidence Co-IP, ubiquitination assays, HIPK2 inhibition/knockdown, Ser36 phospho-site mutagenesis, and a PCOS mouse model

    PMID:40537816

    Open questions at the time
    • Ubiquitin linkage type and direct in vitro reconstitution not shown
    • How phosphorylation blocks RNF121 recognition mechanistically is unresolved
    • Single-lab finding

Open questions

Synthesis pass · forward-looking unresolved questions
  • A unifying model explaining how a secretory-pathway-resident ligase achieves opposing outcomes — degradation versus stabilization, and effects on cytosolic/nuclear processes — remains undefined.
  • No structure of RNF121 engaging a substrate
  • Determinants of degradative versus stabilizing outcomes unknown
  • Ubiquitin-chain topology and E2 partners largely uncharacterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016740 transferase activity 3 GO:0016874 ligase activity 3 GO:0140096 catalytic activity, acting on a protein 3
Localization
GO:0005794 Golgi apparatus 4 GO:0005783 endoplasmic reticulum 3
Pathway
R-HSA-168256 Immune System 2 R-HSA-392499 Metabolism of proteins 2
Complex memberships
GPI transamidase complex

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2010 RNF-121 (C. elegans ortholog) is an ER-membrane-anchored E3 ubiquitin ligase that targets beta-integrin PAT-3 for ERAD-dependent degradation; induction of RNF-121 reduced PAT-3::GFP levels while inhibition caused accumulation of PAT-3::GFP inclusions; genetic epistasis placed RNF-121 downstream of the UPR regulator PERK. C. elegans genetics, RNAi inactivation, GFP reporter assays, genetic epistasis with PERK and ERAD mutants, subcellular localization Molecular biology of the cell High 20357004
2014 Human RNF121 localizes predominantly to the Golgi apparatus and positively regulates NF-κB activation downstream of TNF-α, TLR, NLR, RLR stimulation, and DNA damage; its RING domain catalytic activity is required; RNF121 knockdown impairs IκBα proteasomal degradation without altering RIP1 ubiquitination or IKK activation, and RNF121 co-immunoprecipitates with IκBα but does not directly ubiquitinate it. siRNA library screen (46 transmembrane E3 ligases), NF-κB luciferase reporter assay, RIP1 ubiquitination assay, IKK activation assay, IκBα degradation assay, Co-IP, RING domain mutant analysis Cell communication and signaling : CCS Medium 25388546
2014 Human RNF121 localizes to the Golgi apparatus and its RING domain is required to suppress apoptosis; RNF121 knockdown inhibits cell growth and induces caspase-3-dependent apoptosis, and overexpression of wild-type but not RING-domain mutant RNF121 rescues this phenotype. siRNA knockdown, overexpression of WT vs. RING domain mutants, caspase-3 activation assay, PARP cleavage, pan-caspase inhibitor rescue (Z-VAD-FMK), subcellular localization Acta biochimica et biophysica Sinica Medium 24928685
2015 RNF121 is present in the ER and cis-Golgi and facilitates two opposing fates of voltage-gated sodium channels (NaV): ubiquitin-mediated proteasomal degradation and, when co-expressed with auxiliary NaVβ subunits, membrane localization; loss-of-function mutations in zebrafish rnf121 cause the alligator motility mutant phenotype. Zebrafish forward genetics (alligator mutant), in vivo imaging, NaV channel degradation and localization assays, co-expression with NaVβ subunits, proteasome inhibitor experiments, subcellular fractionation/localization Proceedings of the National Academy of Sciences of the United States of America High 25691753
2015 RNF121 is an ER-localized E3 ubiquitin ligase expressed in endothelial cells that recognizes newly synthesized VEGFR-2 in the ER, ubiquitinates it, and restricts its maturation and cell-surface expression; the RING finger domain is required for this activity; RNF121 overexpression reduces VEGFR-2 surface levels and inhibits VEGF-induced endothelial cell proliferation and angiogenesis, while RNF121 knockdown decreases VEGFR-2 ubiquitination and increases surface VEGFR-2. Co-IP, ubiquitination assay, shRNA knockdown, overexpression, VEGFR-2 maturation (glycosylation) assay, flow cytometry for surface expression, endothelial cell proliferation and angiogenesis assays, RING domain deletion mutant Traffic (Copenhagen, Denmark) High 26602861
2019 RNF121 is required for transcription from AAV capsid-associated genomes but not from transfected plasmids; CRISPR KO of RNF121 causes transcriptional arrest of AAV genomes as shown by RNA Pol ChIP and mRNA half-life measurements; the catalytic RING domain of RNF121 is essential; blocking VCP/p97 completely restores AAV transgene expression in RNF121 KO cells, and DNAPK-Cs is upregulated in KO cells with DNA damage machinery enriched at stalled AAV transcription sites. CRISPR/Cas9 KO, RNA Pol II ChIP, mRNA half-life assay, proteasome/VCP inhibitor rescue, transcriptomic and proteomic analysis, RING domain mutant overexpression rescue PLoS pathogens High 31386698
2022 RNF121 is required for K63-linked polyubiquitination of SARS-CoV-2 ORF7a; knockdown of RNF121 significantly decreased ORF7a binding to TAK1 and NEMO, resulting in suppression of NF-κB activation. RNF121 siRNA knockdown, ubiquitination assay (K63-linked), Co-IP of ORF7a with TAK1/NEMO, NF-κB luciferase reporter assay mBio Medium 35856559
2022 Cryo-EM structure of the human GPI transamidase (GPIT) complex at 3.1 Å resolution reveals RNF121 associated at the back of the complex, interpreted as a quality control factor for the GPIT complex. Single-particle cryo-EM structural determination at 3.1 Å Nature structural & molecular biology Medium 35165458
2024 RNF121 localizes to the cis-Golgi Complex via its transmembrane domain; a point mutation (M158R) in transmembrane helix 4 reduces RNF121 protein stability and abolishes Golgi localization; RNF121 directly binds MYCN protein and enhances its stability; transmembrane helix 5 is required for RNF121-enhanced growth of MYCN-amplified neuroblastoma cells; hemizygous RNF121 deletion reduces TH-MYCN-driven tumorigenicity in vivo. ENU mutagenesis screen, transgenic mouse tumor model, protein localization (immunofluorescence), Co-IP (RNF121–MYCN interaction), MYCN stability assay, domain mutant analysis (helix 5 deletion), hemizygous gene deletion in vivo Communications biology High 39402275
2025 RNF121 acts as an E3 ubiquitin ligase that ubiquitinates CRTC1, targeting it for proteasomal degradation; HIPK2-mediated phosphorylation of CRTC1 at Ser36 prevents this RNF121-dependent ubiquitination, thereby stabilizing CRTC1 and maintaining the CRTC1-CBP-AR transcriptional complex that drives AMH expression. Co-immunoprecipitation, ubiquitination assay, HIPK2 inhibitor/knockdown experiments, phosphorylation-site mutagenesis (Ser36), in vitro and in vivo PCOS mouse model Biology direct Medium 40537816
2012 C. elegans rnf-121 acts at least partially in parallel with rnf-5 and ccdc-55 to promote termination of distal tip cell migration; genetic interaction studies using RNAi and deletion alleles placed rnf-121 in a pathway targeting cell migration-related substrates including beta-integrin PAT-3. C. elegans genetic epistasis, RNAi depletion, deletion allele rnf-121(ok848), DTC migration phenotype scoring Mechanisms of development Medium 22285439

Source papers

Stage 0 corpus · 24 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2022 Ubiquitination of SARS-CoV-2 NSP6 and ORF7a Facilitates NF-κB Activation. mBio 51 35856559
2010 RNF-121 is an endoplasmic reticulum-membrane E3 ubiquitin ligase involved in the regulation of beta-integrin. Molecular biology of the cell 38 20357004
2021 Circ-RNF121 regulates tumor progression and glucose metabolism by miR-1224-5p/FOXM1 axis in colorectal cancer. Cancer cell international 35 34742305
2018 Integrative analysis of oncogenic fusion genes and their functional impact in colorectal cancer. British journal of cancer 31 29955133
2022 Structure of human glycosylphosphatidylinositol transamidase. Nature structural & molecular biology 28 35165458
2019 Ring finger protein 121 is a potent regulator of adeno-associated viral genome transcription. PLoS pathogens 27 31386698
2015 RING finger protein 121 facilitates the degradation and membrane localization of voltage-gated sodium channels. Proceedings of the National Academy of Sciences of the United States of America 24 25691753
2014 The E3 ubiquitin ligase RNF121 is a positive regulator of NF-κB activation. Cell communication and signaling : CCS 22 25388546
2014 RING finger proteins are involved in the progression of barrett esophagus to esophageal adenocarcinoma: a preliminary study. Gut and liver 21 25228972
2009 A 7 Mb region within 11q13 may contain a high penetrance gene for breast cancer. Breast cancer research and treatment 21 19205878
2022 Circular RNA circ-RNF121 contributes to cisplatin (DDP) resistance of non-small-cell lung cancer cells by regulating the miR-646/SOX4 axis. Anti-cancer drugs 16 34387608
2015 RNF121 Inhibits Angiogenic Growth Factor Signaling by Restricting Cell Surface Expression of VEGFR-2. Traffic (Copenhagen, Denmark) 16 26602861
2020 Let-7b-5p is involved in the response of endoplasmic reticulum stress in acute pulmonary embolism through upregulating the expression of stress-associated endoplasmic reticulum protein 1. IUBMB life 14 32534478
2018 Risk analysis of malignant potential of oral verrucous hyperplasia: A follow-up study of 269 patients and copy number variation analysis. Head & neck 14 29377391
2014 Really interesting new gene finger protein 121 is a novel Golgi-localized membrane protein that regulates apoptosis. Acta biochimica et biophysica Sinica 12 24928685
2012 CCDC-55 is required for larval development and distal tip cell migration in Caenorhabditis elegans. Mechanisms of development 11 22285439
2023 Genomic Landscape of Copy Number Variations and Their Associations with Climatic Variables in the World's Sheep. Genes 10 37372436
2024 Identification of SLC35A1 as an essential host factor for the transduction of multi-serotype recombinant adeno-associated virus (AAV) vectors. mBio 5 39601564
2018 Really interesting new gene finger protein 121 is a tumor suppressor of renal cell carcinoma. Gene 5 30149063
2025 Proteomics suggests the role of Cxcl12 secreted by hucMSCs in the treatment of lipopolysaccharide-acute lung injury. Microvascular research 1 40311750
2025 Phosphorylation-stabilized CRTC1 cooperates with CBP and androgen receptor to transactivate AMH expression and drive polycystic ovary syndrome. Biology direct 1 40537816
2024 Golgi-localized Ring Finger Protein 121 is necessary for MYCN-driven neuroblastoma tumorigenesis. Communications biology 1 39402275
2025 RNF121 promotes the proliferation, migration, and invasion of lung cancer cell lines. Cancer genetics 0 41092854
2024 Identification of SLC35A1 as an essential host factor for the transduction of multi-serotype recombinant adeno-associated virus (AAV) vectors. bioRxiv : the preprint server for biology 0 39463973

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