RNF6

RNF6 is a RING-H2 domain E3 ubiquitin ligase that functions as a versatile regulator of protein turnover, cell cycle progression, axon development, and transcription. Its RING domain catalyzes auto-ubiquitination (opposed by the deubiquitinase USP7) and K48-linked polyubiquitination of diverse substrates—including LIMK1, TLE3, FoxA1, SHP-1, p27, CCND2, MST1, QKI, Sqstm1, and NME4—targeting them for proteasomal degradation, while it promotes K63-linked polyubiquitination of the glucocorticoid receptor to stabilize and enhance its transcriptional activity (PMID:16204183, PMID:29374067, PMID:35926709, PMID:39918413, PMID:31645658). Beyond its E3 ligase function, RNF6 acts as a nuclear transcriptional regulator that directly binds promoter DNA—including the Inha, CCNA1, CREBBP, and SKP2 promoters—through a region containing a KIL motif, activating gene expression programs relevant to growth control and cell cycle regulation (PMID:11971979, PMID:37904524, PMID:39938447). Through substrate-specific ubiquitination, RNF6 modulates Wnt/β-catenin, SHP-1/STAT3, androgen receptor, Hippo/YAP, and JNK/c-JUN signaling pathways across multiple cancer contexts, and regulates local actin dynamics in neurons via LIMK1 degradation (PMID:19345326, PMID:30323630, PMID:34970341, PMID:41616518).

1. 1999 Medium

   Initial cloning established RNF6 as a novel RING-H2 finger protein with an N-terminal coiled-coil domain and a KIL motif upstream of its RING domain, providing the structural framework for its subsequent characterization as an E3 ligase and transcription factor.

   Evidence cDNA cloning, sequence analysis, and FISH mapping to 13q12.2

   PMID:10331950

   Open questions at the time

   • No enzymatic activity demonstrated at this stage
   • KIL motif function unknown
   • No substrates or binding partners identified
2. 2002 Medium

   Before its E3 ligase activity was established, RNF6 was shown to localize to PML/Daxx nuclear bodies and function as a transcriptional regulator that directly binds GGGGC repeats in the Inha promoter, restoring growth control in Sertoli tumor cells.

   Evidence EMSA/DNA binding, immunofluorescence co-localization with PML/Daxx, luciferase reporter in Sertoli cell line

   PMID:11971979

   Open questions at the time

   • DNA-binding domain not precisely mapped
   • Relationship between RING E3 activity and transcriptional function unexplored
   • Single cell system tested
3. 2005 High

   The first substrate of RNF6 E3 ligase activity was identified: RNF6 polyubiquitinates LIMK1 for proteasomal degradation in axonal growth cones, establishing RNF6 as a regulator of local actin dynamics and axon outgrowth through genetic epistasis experiments.

   Evidence RNAi in primary hippocampal neurons, Co-IP, ubiquitination assay, proteasome inhibitor rescue, LIMK1 modulation rescue

   PMID:16204183

   Open questions at the time

   • Whether RNF6 regulates other cytoskeletal substrates in neurons unknown
   • Ubiquitin chain linkage type not specified
   • Upstream signals activating RNF6 in neurons unidentified
4. 2009 High

   RNF6 was revealed to ubiquitinate the androgen receptor not for degradation but to modulate AR transcriptional specificity—mutation of AR ubiquitination sites selectively altered AR target gene expression and coactivator recruitment—expanding RNF6's repertoire beyond degradative ubiquitination.

   Evidence Co-IP/MS proteomic screen, ubiquitination assay, AR site-directed mutagenesis, ChIP, luciferase reporter

   PMID:19345326

   Open questions at the time

   • Ubiquitin chain type mediating transcriptional modulation not fully defined
   • Whether this non-degradative mechanism applies to other RNF6 substrates unknown
5. 2018 High

   Three new degradative substrates—TLE3, FoxA1, and SHP-1—were identified, linking RNF6 to Wnt/β-catenin activation (via TLE3 degradation releasing β-catenin onto TCF4/LEF), EMT/metastasis (via FoxA1 degradation), and STAT3 signaling (via SHP-1 degradation sustaining pSTAT3), establishing RNF6 as a multi-pathway oncogenic E3 ligase.

   Evidence Co-IP, ubiquitination assays, functional rescue with substrate re-expression, xenograft and metastasis models, luciferase reporters

   PMID:29374067 PMID:30323630 PMID:30496760

   Open questions at the time

   • Whether these substrates compete for RNF6 binding unknown
   • Tissue-specific regulation of substrate selectivity not addressed
   • SHP-1 study from single lab with limited orthogonal validation
6. 2019 Medium

   RNF6 was shown to promote K63-linked (stabilizing) polyubiquitination of the glucocorticoid receptor, enhancing GR stability and transcriptional activity in myeloma cells—demonstrating that RNF6 can employ different ubiquitin chain types to achieve opposing outcomes on substrate fate.

   Evidence Co-IP, K63-linkage-specific ubiquitination assay, luciferase reporter, western blot for GR stability

   PMID:31645658

   Open questions at the time

   • Structural basis for K63 vs K48 chain-type specificity unknown
   • Whether an E2-switching mechanism determines chain type not tested
   • Single lab study
7. 2022 High

   Reconstituted in vitro ubiquitination with RING domain mutagenesis established that RNF6 auto-ubiquitinates in a RING-dependent manner, and mass spectrometry identified USP7 as the deubiquitinase that stabilizes RNF6 by removing K48-linked chains, defining the RNF6 self-regulatory circuit.

   Evidence Reconstituted in vitro ubiquitination, C632S/C635S mutagenesis, tandem mass spectrometry, USP7 inhibitor treatment

   PMID:35926709

   Open questions at the time

   • Physiological signals that modulate USP7–RNF6 interaction not identified
   • Whether other DUBs contribute to RNF6 stabilization untested
8. 2022 Medium

   The KIL domain was mapped as the p27 interaction interface, and RNF6 was shown to degrade p27 in early G0/G1 to activate CDK2/Cyclin E and drive cell cycle entry; concurrently, RNF6-mediated QKI degradation in macrophages was linked to PI3K-dependent autophagy for pathogen clearance, expanding RNF6 substrates into immune and cell cycle contexts.

   Evidence KIL domain Co-IP, ubiquitination assays, FACS cell cycle analysis, iTRAQ MS, RNA immunoprecipitation, myeloid-specific QKI KO mice

   PMID:35456636 PMID:36088389

   Open questions at the time

   • Whether KIL domain mediates interaction with other substrates beyond p27 unknown
   • Structural basis of KIL-substrate recognition not determined
9. 2023 Medium

   ChIP-seq in gastric cancer cells established that RNF6 functions genome-wide as a transcription factor, directly binding promoters of CCNA1 and CREBBP to activate their expression, confirming the dual E3 ligase/transcription factor nature first suggested by the 2002 Inha study.

   Evidence ChIP-seq, ChIP-PCR, luciferase promoter reporter, siRNA knockdown with functional rescue

   PMID:37904524

   Open questions at the time

   • DNA-binding domain not structurally resolved
   • Whether transcriptional and E3 ligase functions are coordinated or independent unclear
   • Genome-wide binding sites validated for only two targets
10. 2025 High

    CCND2 was identified as a direct RNF6 substrate via K48-linked ubiquitination dependent on Thr280, causing G1 arrest in lung adenocarcinoma; separately, RNF6 was shown to degrade p27 both directly and indirectly by transcriptionally activating SKP2, revealing a multi-layered strategy for cell cycle control.

    Evidence AP-MS, in vitro ubiquitination, T280 mutagenesis, ΔRING mutagenesis, SKP2 promoter luciferase reporter, xenograft models

    PMID:39918413 PMID:39938447

    Open questions at the time

    • Kinase phosphorylating CCND2 Thr280 to prime RNF6 recognition not identified
    • Relative contribution of direct p27 ubiquitination vs SKP2-mediated degradation not quantified
11. 2025 Medium

    RNF6 was linked to autophagy regulation and barrier integrity through site-specific ubiquitination of Sqstm1 at K314, and to innate antiviral immunity through interaction with ZIKV NS5 and negative regulation of type I interferon signaling.

    Evidence Site-specific ubiquitination assay (K314), autophagy inhibitor rescue, CRISPR screen, RNF6 KO/KD/OE with viral replication readout, Co-IP with NS5

    PMID:40231770 PMID:41902231

    Open questions at the time

    • Sqstm1 K314 ubiquitin chain type not specified
    • Mechanism by which RNF6 suppresses interferon signaling not delineated
    • Whether NS5 is a substrate or a co-opted interactor unknown
12. 2026 Medium

    NME4 was identified as an RNF6 substrate degraded via K48-linked ubiquitination, with NME4 loss activating JNK/c-JUN signaling in ovarian cancer, adding another pathway axis to RNF6's oncogenic repertoire.

    Evidence Co-IP, CHX chase, K48-linkage-specific ubiquitination assay, NME4 knockdown rescue, xenograft model

    PMID:41616518

    Open questions at the time

    • Degron motif on NME4 not mapped
    • Whether NME4 degradation is context-specific or constitutive unknown

• Key unresolved questions include: the structural basis for RNF6's dual function as E3 ligase and DNA-binding transcription factor, the mechanism determining K48 vs K63 ubiquitin chain-type selection across substrates, the identity of the DNA-binding domain, and how upstream signals regulate RNF6 substrate selectivity in different tissues.
• No crystal or cryo-EM structure of RNF6
• No systematic analysis of E2 partners determining chain specificity
• Tissue-specific substrate hierarchy undefined