NOL4 is a 524 amino acid protein that is predominantly expressed in testis and brain. NOL4 contains at least two domains that direct it to subnuclear locations. The gene encoding NOL4 is located on human chromosome 18, which houses over 300 protein-coding genes and contains nearly 76 million bases. There are a variety of diseases associated with defects in chromosome 18-localized genes, some of which include Trisomy 18 (also known as Edwards syndrome), Niemann-Pick disease, hereditary hemorrhagic telangiectasia, erythropoietic protoporphyria and follicular lymphomas. There are two isoforms of NOL4 that are produced as a result of alternative splicing events.