STRUCTURAL ORGANIZATION OF THE HUMAN SHORT-CHAIN L-3-HYDROXYACYL-COA DEHYDROGENASE GENE

The third step in the mitochondrial P-oxidation spiral of short-chain fatty acids is catalyzed by short-chain L-3-hydroxyacyl-CoA dehydrogen ase (HADHSC; EC 1.1.1.35). We have determined the structural organizat ion of the human HADHSC gene by sequencing of cloned genomic amplifica tion products, obtained using HADHSC-specific cDNA-based primers, as w ell as by direct sequencing of an isolated PAC clone containing the HA DHSC gene. Upon comparison with the HADHSC cDNA sequence, HADHSC was s hown to encompass at least eight exons, ranging in size from 73 to 158 bp, and 7 introns. The total HADHSC gene spans approximately 49 kb. T he HADHSC 5'-flanking region was characterized with an AluI plasmid li brary constructed from a partially AluI-digested PAC clone containing the human HADHSC gene. Several typical promoter elements such as a CAA T-box, Sp1, AP1, and AP2 sites were found, while a TATA-box was appare ntly absent. Among other putative regulatory elements, a NRRE-1 site w as identified. By radiation hybrid panel, assisted fine-mapping HADHSC was linked to marker AFM070TH5, corresponding to Chromosome (Chr) 4q2 2-26, and a putative HADHSC pseudogene was linked to marker D15S1324, located at Chr 15q17-21. Knowledge of the genomic organization and 5'- flanking region of HADHSC will enable genomic mutation analysis of pat ients suspected of HADHSC deficiency, as well as facilitate the invest igation into the transcriptional regulation of short-chain fatty acid oxidizing gene products in general and HADHSC expression in particular .