NAE1/UBA3-UBE2M are E1 and E2 enzymes for the URM1 modification

Area of Science:

• Biochemistry
• Molecular Biology
• Cellular Biology

Background:

• Ubiquitin-related modifier 1 (URM1) is a conserved ubiquitin-like protein with dual roles in tRNA modification and protein modification.
• URM1 is hypothesized as a primitive modifier and a potential precursor to the ubiquitin system.
• The specific enzymes (E1, E2, E3) involved in the human URM1 modification cascade remained unidentified.

Purpose of the Study:

• To identify the enzymes responsible for the URM1 modification cascade in human cells.
• To investigate the role of URM1 in cellular response to oxidative stress.
• To explore the therapeutic potential of targeting the URM1 pathway in liver cancer.

Main Methods:

• Development of an activity-based URM1 probe to capture cysteine enzymes.
• Proteomic characterization and cell-based validation of identified enzymes.
• Bioinformatic analysis of gene expression changes upon knockdown of URM1 pathway components.
• Pharmacological inhibition of the URM1 pathway and assessment of synergy with cisplatin in liver cancer cells.

Main Results:

• Identification of NAE1/UBA3 as the E1 enzyme and UBE2M as the E2 enzyme for the URM1 conjugation pathway.
• Evidence suggesting DCN1 involvement in URM1 conjugation.
• URM1 plays a protective role against oxidative stress.
• Genetic knockdown of NAE1, UBE2M, or URM1 impacts genes related to stress response and liver diseases.
• Pevonedistat (NAE1 inhibitor) synergizes with cisplatin to kill liver cancer cells.

Conclusions:

• The study elucidates the enzymatic machinery of the URM1 conjugation pathway, identifying NAE1/UBA3 and UBE2M as key components.
• URM1 is crucial for cellular defense against oxidative stress and is implicated in liver disease pathways.
• Targeting the URM1 pathway, particularly with NAE1 inhibitors like Pevonedistat, shows promise for synergistic cancer therapy, especially in liver cancer.