An unprocessed pseudogene of inducible nitric oxide synthase gene in human.

Inducible nitric oxide synthase (iNOS or NOSII) is one of three distinct NOS isoforms in human. The NOSII isoform is expressed in a variety of cells and tissues in response to endotoxins and cytokines. The human genome contains at least two loci for the NOSII gene, one of which (NOSII-1) has previously been assigned to proximal region of the long arm (cen-q11.2 or q11.2-q12) or to pericentric (p11-q11) regions of chromosome 17. The present study, carried out using fluorescence in situ hybridization (FISH) method, shows that a pseudogene gene (NOSII-2) is mapped to chromosome 17q11.2 site. The NOSII-2 sequence contains the exon and intron sequences present in NOSII-1 but with several mutations such as single base substitutions, additions, and deletions. Additionally, the NOSII-2 sequence also contains an incomplete reductase domain which corresponds only to the cofactor binding sites without the oxygenase domain that carry heme and substrate binding sites. NOSII-2, therefore, appears to be an unprocessed pseudogene, which cannot be translated to a functional enzyme because of its incomplete sequences and mutations.