STRUCTURAL ORGANIZATION AND CHROMOSOMAL ASSIGNMENT OF THE HUMAN OBESEGENE

The obese (ob) gene has been identified through a positional cloning a pproach; the mutation of this gene causes marked hereditary obesity an d diabetes mellitus in mice, We report here the isolation and characte rization of the human ob gene, Southern blot analysis demonstrated a s ingle copy of the ob gene in the human genome, The human ob gene spann ed similar to 20 kilobases (kb) and contained three exons separated by two introns, The first intron, similar to 10.6 kb in size, occurred i n the 5'-untranslated region, 29 base pair (bp) upstream of the ATG st art codon, The second intron of 2.3 kb in size was located at glutamin e +49, By rapid amplification of 5'-cDNA ends, the transcription initi ation sites were mapped 54 similar to 57 bp upstream of the ATG start codon, The 172-bp 5'-flanking region of the human ob gene contained a TATA box-like sequence and several cis-acting regulatory elements (thr ee copies of GC boxes, an AP-2-binding site, and a CCAAT/enhancer-bind ing protein-binding site), By the fluorescence in situ hybridization t echnique, the ob gene was assigned to human chromosome 7q31.3. This st udy should establish the genetic basis for ob gene research in humans, thereby leading to the better understanding of the molecular mechanis ms underlying the ob gene.