UBE2G2

UBE2G2 Full Name

ubiquitin-conjugating enzyme E2G 2

UBE2G2 Introduction

Ubiquitin-conjugating enzyme E2G 2 (UBE2G2), also known as Ubc7, is an endoplasmic reticulum (ER)-associated E2 ubiquitin-conjugating enzyme that functions in the endoplasmic reticulum-associated degradation (ERAD) pathway, a quality control system that eliminates misfolded, misassembled, or excess proteins from the ER. Encoded by the UBE2G2 gene on chromosome 21q22.3, UBE2G2 is a tail-anchored membrane protein with its catalytic UBC domain oriented toward the cytosol, where it collaborates with ER-resident E3 ubiquitin ligases to ubiquitinate ERAD substrates targeted for proteasomal degradation.

Figure 1. Strcuture of UBE2G2.

ERAD Pathway and Ubiquitin Chain Assembly at the ER Membrane
UBE2G2 functions downstream of the ERAD recognition and retrotranslocation steps, which involve the identification of misfolded luminal or membrane proteins and their extraction (dislocation) from the ER membrane into the cytosol through a protein-conducting channel containing the E3 ligase HRD1 (SYVN1). Once cytosolic portions of the substrate are exposed, UBE2G2, together with its partner E2 enzyme UBE2J1 (Ubc6e), catalyzes the polyubiquitination of substrate lysine residues, targeting the protein for recognition and degradation by the 26S proteasome. UBE2G2 is specifically recruited to the HRD1 E3 ligase complex through an interaction with the ER membrane protein AUP1 (ancient ubiquitous protein 1), which serves as a platform for UBE2G2 assembly at the ER membrane. A notable biochemical property of UBE2G2 is its ability to synthesize K48-linked polyubiquitin chains processively when partnered with the E3 ligase gp78 (AMFR), a process facilitated by the interaction of UBE2G2's C-terminal tail region with the gp78 coupling ubiquitin-binding (CUE) domain, which allosterically activates UBE2G2 for efficient chain elongation.

UBE2G2 in ER Stress, Protein Misfolding Diseases, and Cancer
UBE2G2-mediated ERAD is essential for maintaining ER proteostasis and preventing the accumulation of misfolded proteins that trigger ER stress and the unfolded protein response (UPR). Impaired ERAD due to UBE2G2 deficiency or dysfunction contributes to the pathogenesis of diseases characterized by protein misfolding and aggregation, including certain neurodegenerative disorders. In cancer, UBE2G2 expression is frequently dysregulated: it is overexpressed in hepatocellular carcinoma, where enhanced ERAD capacity may support the high secretory protein load of transformed hepatocytes and confer tolerance to chronic ER stress. UBE2G2 has also been identified as a dependency gene in certain cancer cell lines that are particularly reliant on ERAD for survival, including multiple myeloma cells with high immunoglobulin production. Pharmacological inhibition of the ubiquitin-proteasome system with proteasome inhibitors (e.g., bortezomib) is an established therapeutic strategy in multiple myeloma that exploits the heavy reliance of these cells on ERAD for survival. More selective targeting of UBE2G2 or its partner E3 ligases is under investigation as a strategy to achieve proteotoxic stress selectively in cancer cells while sparing normal cells with lower ER protein-folding demands.

Alternate Names for UBE2G2

UBE2G2; ubiquitin-conjugating enzyme E2G 2; ubiquitin conjugating enzyme E2G 2 (homologous to yeast UBC7); ubiquitin conjugating enzyme E2G 2 (UBC7 homolog, yeast); ubiquitin-conjugating enzyme E2 G2; UBC7; ubiquitin-protein ligase G2; ubiquitin carrier protein G2; ubiquitin conjugating enzyme 7; ubiquitin conjugating enzyme G2