FAU is a ubiquitously expressed gene encoding a fusion protein of ribosomal protein S30 and a ubiquitin-like domain 1. As a structural component of the 40S ribosomal subunit, FAU contributes to ribosomal assembly and function in cytosolic translation 1. Beyond its canonical ribosomal role, FAU exhibits pro-apoptotic activity, with both human and marine sponge FAU homologues increasing apoptosis in cultured cells 2. The ubiquitin-like domain suggests FAU participates in protein ubiquitination and modification-dependent protein catabolism. FAU is significantly down-regulated in human prostate, breast, and ovarian cancers, with dysregulation associated with poor breast cancer prognosis 2. This cancer-associated dysregulation appears evolutionarily conserved, as FAU function in apoptosis and cancer biology is preserved across metazoans from early-branching sponges to mammals 2. These dual functions—ribosomal structural protein and apoptosis regulator—suggest FAU serves as a tumor suppressor, making it clinically relevant for cancer diagnosis and prognosis. The evolutionary conservation of FAU's cancer-related functions provides a framework for investigating its role in human carcinogenesis.