MEX3C (mex-3 RNA binding family member C) is a dual-function RNA-binding protein and E3 ubiquitin ligase that regulates gene expression through both post-transcriptional mRNA control and protein degradation mechanisms 1. The protein binds to 3' UTRs of target mRNAs and promotes their decay through recruitment of deadenylation machinery, with RNA binding sufficient to prevent translation while ubiquitin ligase activity is required for complete mRNA degradation 1. In cancer contexts, MEX3C demonstrates oncogenic properties by targeting tumor suppressor pathways - it degrades SOCS3 mRNA to activate JAK2/STAT3 signaling in hepatocellular carcinoma metastasis 1 and promotes RUNX3 ubiquitination and degradation in lung adenocarcinoma 2. MEX3C also modulates immune responses, correlating with immune checkpoint gene expression and promoting M2 macrophage polarization while suppressing M1 activation 3. Additionally, MEX3C participates in extracellular vesicle biology through interaction with adaptor protein complex AP-2, facilitating selective microRNA sorting into exosomes 4. In metabolic regulation, MEX3C controls adiposity and physical activity through neuronal mechanisms 5. The consistent upregulation of MEX3C across multiple cancer types and its association with poor prognosis suggests potential as both a biomarker and therapeutic target 67.