Dcun1D3 is a 304 amino acid protein that contains one Dcun1 domain. The Dcun1 domain is an approximately 190 residue module that is thought to have the features of a basic helix-loop-helix leucine zipper domain, a domain commonly found in transcription factors. It has been suggested that Dcun1D3 may be involved in cell cycle progression and cell growth. The gene that encodes Dcun1D3 maps to human chromosome 16, which encodes over 900 genes in approximately 90 million base pairs, makes up nearly 3% of human cellular DNA and is associated with a variety of genetic disorders. The GAN gene is located on chromosome 16 and, with mutation, may lead to giant axonal neuropathy, a nervous system disorder characterized by increasing malfunction with growth. Chromosome 16 houses the CREBBP gene that encodes a critical CREB binding protein that is responsible for the Rubinstein-Taybi syndrome, a rare disorder characterized by mental retardation and predisposition to tumor growth and white blood cell neoplasias.