May have pro-apoptotic activity. Component of the 40S subunit of the ribosome. Contributes to the assembly and function of 40S ribosomal subunits. Component of the 40S subunit of the ribosome. FUBI is cleaved from ribosomal protein S30 by the deubiquitinase USP36 before the assembly of ribosomal protein S30 into pre-40S ribosomal particles. FUBI removal from ribosomal protein S30 is a crucial event for the final maturation of pre-40S particles. FAU encodes a fusion protein consisting of the ubiquitin-like protein FUBI at the N terminus and ribosomal protein S30 at the C terminus. Lacks the typical lysine residues that participate in Ub's polyubiquitination. However contains a C-terminal di-glycine signature after its proteolytic separation from ribosomal protein S30 and could theoretically be conjugated onto target proteins. In the N-terminal section; belongs to the ubiquitin family. In the C-terminal section; belongs to the eukaryotic ribosomal protein eS30 family.