The function of MEX3C (mex-3 RNA binding family member C, ENSG00000176624) is as follows. E3 ubiquitin ligase responsible for the post-transcriptional regulation of common HLA-A allotypes. Binds to the 3' UTR of HLA-A2 mRNA, and regulates its levels by promoting mRNA decay. RNA binding is sufficient to prevent translation, but ubiquitin ligase activity is required for mRNA degradation. {ECO:0000269|PubMed:22863774, ECO:0000269|PubMed:23446422}.