NPM1 encodes a phosphoprotein which moves between the nucleus and the cytoplasm. The gene product is thought to be involved in several processes including regulation of the ARF/p53 pathway. A number of genes are fusion partners have been characterized, in particular the anaplastic lymphoma kinase gene on chromosome 2. Mutations in NPM1 are associated with acute myeloid leukemia. More than a dozen pseudogenes of NPM1 have been identified. Alternative splicing results in multiple transcript variants.