Ubiquitin-Conjugating Enzyme UBE2N Modulates Proteostasis in Immunoproteasome-Positive Acute Myeloid Leukemia

Authors

Chiharu Ishikawa
Laura Barreyro
Avery M Sampson
Kathleen M Hueneman
Kwangmin Choi
Sophia Y Philbrook
Issac Choi
Lyndsey C Bolanos
Mark Wunderlich
Andrew G Volk
Stephanie S Watowich
Kenneth D Greis
Daniel T Starczynowski

Publication Date

5-15-2025

Journal

Journal of Clinical Investigation

Abstract

Altered protein homeostasis through proteasomal degradation of ubiquitinated proteins is a hallmark of many cancers. Ubiquitination, coordinated by E1, E2, and E3 enzymes, involves up to 40 E2-conjugating enzymes in humans to specify substrates and ubiquitin linkages. In a screen for E2 dependencies in acute myeloid leukemia (AML), ubiquitin conjugating enzyme E2 N (UBE2N) emerged as the top candidate. To investigate UBE2N's role in AML, we characterized an enzymatically defective mouse model of UBE2N, revealing UBE2N's requirement in AML without an impact on normal hematopoiesis. Unlike other E2s, which mediate lysine-48 (K48) polyubiquitination and degradation of proteins, UBE2N primarily synthesizes K63-linked chains, stabilizing or altering protein function. Proteomic analyses and a whole-genome CRISPR-activation screen in pharmacologically and genetically UBE2N-inhibited AML cells unveiled a network of UBE2N-regulated proteins, many of which are implicated in cancer. UBE2N inhibition reduced their protein levels, leading to increased K48-linked ubiquitination and degradation through the immunoproteasome and revealing UBE2N activity is enriched in immunoproteasome-positive AML. Furthermore, an interactome screen identified tripartite motif-containing protein 21 (TRIM21) as the E3 ligase partnering with activated UBE2N in AML to modulate UBE2N-dependent proteostasis. In conclusion, UBE2N maintains proteostasis in AML by stabilizing target proteins through K63-linked ubiquitination and prevention of K48 ubiquitin-mediated degradation by the immunoproteasome. Thus, inhibition of UBE2N catalytic function suppresses leukemic cells through selective degradation of critical proteins in immunoproteasome-positive AML.

Keywords

Ubiquitin-Conjugating Enzymes, Leukemia, Myeloid, Acute, Animals, Mice, Proteostasis, Humans, Proteasome Endopeptidase Complex, Ubiquitination, Neoplasm Proteins, Mice, Knockout, Hematology, Leukemias, Oncology, Ubiquitin-proteosome system

DOI

10.1172/JCI184665

PMID

40371639

PMCID

PMC12077902

PubMedCentral® Posted Date

5-15-2025

PubMedCentral® Full Text Version

Post-print

Published Open-Access

yes