MOLECULAR-CLONING, STRUCTURE, AND CHROMOSOMAL LOCALIZATION OF THE HUMAN INDUCIBLE NITRIC-OXIDE SYNTHASE GENE

Nitric oxide, a multifunctional effector molecule synthesized by nitri c oxide synthase (NOS) from L-arginine, conveys signals for vasorelaxa tion, neurotransmission, and cytotoxicity. Three different NOS isoform s have been identified which fall into two distinct types, constitutiv e and inducible. The inducible NOS (iNOS) isoform is expressed in a va riety of cell types and tissues in response to inflammatory agents and cytokines, The human iNOS (NOS2) gene was isolated on overlapping cos mid clones from a human genomic library using both the murine macropha ge and the human hepatocyte iNOS cDNAs as probes, Ah isolated cosmids were part of a single genomic locus and no other genomic loci were ide ntified or isolated. Analysis of this locus indicated that the human i NOS gene is similar to 37 kilobases in length and consists of 26 exons and 25 introns. Primer extension analysis of lipopolysaccharide and c ytokine-stimulated human hepatocyte RNA mapped the transcriptional ini tiation site 30 base pairs downstream of a TATA sequence, and a 400-ba se pair 5'-flanking region was found to be structurally similar to the recently described murine iNOS promoter. Polymerase chain reaction an alysis of a human/rodent genomic DNA somatic cell hybrid panel and flu orescent in situ hybridization indicated that the human iNOS gene is l ocated on chromosome 17 at position 17cen-q11.2.