Structural organization of the human isovaleryl-CoA dehydrogenase gene.

Isovaleryl-CoA dehydrogenase (IVD) catalyzes the third step in leucine catabolism. The genetic deficiency of IVD causes isovaleric acidemia. The functional IVD gene spans approximately 15 kb and consists of 12 exons and 11 introns, with the exon size ranging from 52 to 728 bp. The poly(A) addition site begins 21 nucleotides downstream of this signal. The 5'-flanking region contained typical promoter elements such as TATA and CAT boxes in addition to other putative regulatory sequences. The transcription start site appeared to be located 344 bp upstream of the initiator methionine codon. The GC content in this region is very high. In Northern blot analysis, the IVD cDNA probe hybridized to three RNA species of sizes 2.1, 3.6, and 4.8 kb, respectively. The 2.1-kb band corresponds to the size of IVD cDNA. The results from experiments using an IVD-specific oligomer and stringent washes with 3.0 M tetramethylammonium chloride suggested that high GC content may have caused hybridization of the probe to the 3.6- and 4.8-kb species.