Mammalian ribosomal proteins are encoded by multigene families that consist of processed pseudogenes and one functional intron-containing gene within their coding regions. Ribosomal Protein S20, also known as RPS20, is a 119 amino acid cytoplasmic protein that is a component of the 40S ribosomal subunit. Co-transcribed with the small nucleolar RNA gene U54, Ribosomal Protein S20 is a primary binding protein (it binds independently to its target protein) that interacts with both the 5’ and 3’