EEFSEC is a 596 amino acid protein that localizes to both the nucleus and the cytoplasm and belongs to the GTP-binding elongation factor family. Functioning as a translation factor, SELB binds GTP and GDP and is necessary for the incorporation of selenocysteine into target proteins. The gene encoding SELB maps to human chromosome 3, which houses over 1,100 genes, including a chemokine receptor (CKR) gene cluster and a variety of human cancer-related gene loci. Key tumor suppressing genes on chromosome 3 include those that encode the apoptosis mediator RASSF1, the cell migration regulator HYAL1 and the angiogenesis suppressor SEMA3B. Marfan Syndrome, porphyria, von Hippel-Lindau syndrome, osteogenesis imperfecta and Charcot-Marie-Tooth Disease are a few of the numerous genetic diseases associated with chromosome 3.