Ribosomes, the organelles that catalyze protein synthesis, are composed of a small subunit (40S) and a large subunit (60S) that consist of over 80 distinct ribosomal proteins. Mammalian ribosomal proteins are encoded by multigene families that contain processed pseudogenes and one functional intron-containing gene within their coding regions. Ribosomal Protein L15, also known as RPL15, EC45 or RPLY10, is a 204 amino acid protein that localizes to the cytoplasm and functions as a component of the 60S subunit, playing a role in protein translation. Existing as multiple alternatively spliced isoforms, Ribosomal Protein L15 is overexpressed in esophageal and gastric tumors, suggesting a role in carcinogenesis. Like most ribosomal proteins, Ribosomal Protein L9 exists as multiple processed pseudogenes that are scattered throughout the genome.