UBE2F

UBE2F is a neddylation E2 conjugating enzyme that, in partnership with the E3 SAG/RBX2, catalyzes NEDD8 conjugation onto CUL5 to activate CRL5 (Cullin-RING Ligase 5) ubiquitin ligase complexes, a node that governs cell survival, proliferative signaling, immune cell fate, and viral replication (PMID:27591266, PMID:39762645). Active CRL5 directs degradation of multiple substrates: it ubiquitylates the pro-apoptotic protein NOXA via K11-linked (rather than K48-linked) chains to suppress apoptosis (PMID:27591266), and through a CRL5-ASB11 complex it ubiquitylates and degrades the RAS-family tumor suppressor DIRAS2, thereby sustaining MAPK-c-Myc signaling (PMID:38574733). Beyond cullin substrates, UBE2F together with SAG/RBX2 neddylates the small GTPase RHEB at K169, enhancing its lysosomal localization and GTP-binding affinity to drive mTORC1 activation and Pten-loss-driven hepatic steatosis and tumorigenesis (PMID:39762645). UBE2F activity is itself constrained by a counter-regulatory neddylation E2, UBE2M, which acts as a ubiquitylation E2 for the Parkin-DJ-1 E3 ligase to target UBE2F for degradation under stress, linking the two E2s in a negative feedback axis that controls NOXA levels (PMID:29932898). Through the CUL5 axis UBE2F also restrains JUNB accumulation and IL-2Rβ expression to set IL-15 sensitivity and self-renewal of CD8 T cells (PMID:42188874), and is required for pseudorabies virus replication (PMID:41478481). UBE2F is pharmacologically tractable: the small molecule HA-9104 binds UBE2F, lowers its protein level, and inactivates CRL5 to trigger NOXA-dependent apoptosis (PMID:36253371).

1. 2016 High

   Established UBE2F's core enzymatic role by showing it forms a tri-complex with SAG/RBX2 and CUL5 to neddylate CUL5 and activate CRL5, defining a survival pathway via NOXA degradation.

   Evidence Pulldown, in vivo/in vitro ubiquitylation assays, K11R linkage-specific mutagenesis, and NOXA knockdown epistasis

   PMID:27591266

   Open questions at the time

   • Did not address non-CUL5 neddylation substrates
   • Physiological contexts beyond cancer cells unexplored
2. 2018 High

   Revealed how UBE2F levels are controlled, identifying UBE2M as a dual-activity E2 that drives UBE2F ubiquitylation/degradation via Parkin-DJ-1, creating a negative regulatory axis between the two neddylation E2s.

   Evidence Biochemical assays defining UBE2M dual activity, genetic knockdown/overexpression with lung cancer growth readout

   PMID:29932898

   Open questions at the time

   • Stress signals that trigger UBE2M switch to ubiquitylation E2 not fully defined
   • Direct E3-substrate contacts on UBE2F not mapped
3. 2020 Medium

   Connected UBE2F stability to chemoresistance, showing platinum disrupts UBE2F-RBX1 association to reduce UBE2F degradation, driving CRL5 activation and apoptosis resistance.

   Evidence Co-IP of UBE2F-RBX1, immunoblotting, UBE2F knockout sensitization assays, NOXA protein readout

   PMID:33184273

   Open questions at the time

   • Single-lab evidence
   • Mechanism by which platinum perturbs the UBE2F-RBX1 interface unresolved
4. 2022 Medium

   Demonstrated UBE2F is druggable by identifying HA-9104, a direct-binding small molecule that depletes UBE2F and inactivates CRL5 to induce apoptosis.

   Evidence Structure-based virtual screen, direct binding assay, CUL5 neddylation and NOXA accumulation readouts, xenograft models

   PMID:36253371

   Open questions at the time

   • Binding-site/structural basis of HA-9104 engagement not resolved
   • Selectivity over other E2s not established
5. 2024 High

   Extended the CRL5 substrate repertoire in vivo, showing UBE2F-driven CRL5-ASB11 degrades DIRAS2 to sustain MAPK-c-Myc signaling and tumor growth.

   Evidence KrasG12D PDAC mouse model with Ube2f conditional deletion, DIRAS2 ubiquitylation assays, Diras2 deletion epistatic rescue

   PMID:38574733

   Open questions at the time

   • Whether ASB11 is the sole substrate receptor for DIRAS2 unclear
   • Generality across other tumor types untested
6. 2025 High

   Uncovered a non-cullin neddylation substrate, showing UBE2F/SAG neddylates RHEB at K169 to enhance lysosomal localization, GTP binding, and mTORC1 activation in liver tumorigenesis.

   Evidence K169 site-specific neddylation/mutagenesis, lysosomal fractionation, GTP-binding assay, mTORC1 readout, liver-specific Ube2f KO mouse

   PMID:39762645

   Open questions at the time

   • Whether other GTPases are neddylated substrates unknown
   • Crosstalk between RHEB neddylation and CRL5 substrate flux not addressed
7. 2025 Medium

   Showed UBE2F-RBX2-mediated CUL5 neddylation is required for pseudorabies virus replication, implicating the pathway in host-virus biology.

   Evidence shRNA knockdown of UBE2F/RBX2, pharmacological CUL5 neddylation inhibition, PRV replication assay

   PMID:41478481

   Open questions at the time

   • Single-lab evidence
   • CRL5 substrate(s) mediating the proviral effect not identified
8. 2026 Medium

   Defined an immune-cell function, showing UBE2F-dependent CUL5 neddylation restrains JUNB/IL-2Rβ to tune IL-15 sensitivity and CD8 T cell self-renewal and survival.

   Evidence Genetic UBE2F ablation in CD8 T cells, CUL5 neddylation assay, JUNB/IL-2Rβ readouts, viral and tumor control models

   PMID:42188874

   Open questions at the time

   • Single-lab evidence
   • CRL5 substrate receptor controlling JUNB not pinpointed

• How UBE2F substrate specificity is partitioned between cullin (CUL5) and non-cullin (RHEB) targets, and the structural basis of its E2-E3 pairing and pharmacological inhibition, remain open.
• No structural model defining UBE2F substrate-selection determinants
• Full non-cullin substrate set unknown
• Tissue-specific regulation of UBE2F abundance incompletely mapped