Characterization of the HSD17B4 gene: D-specific multifunctional protein 2/17beta-hydroxysteroid dehydrogenase IV

The HSD17B4 gene codes for a 80 kDa multifunctional enzyme containing three distinct functional domains and is localized in peroxisomes. The N-terminal part exhibits 3-hydroxyacyl-CoA dehydrogenase and 17beta-hydroxysteroid dehydrogenase activity whereas the central part shows enoyl-CoA hydratase activity. The carboxy-terminal part of the protein has sterol-carrier-protein activity. The protein is widely expressed, however in several tissues like brain, uterus and lung its expression is limited to specific cells like Purkinje cells or luminal epithelium. The HSD17B4 gene consist of 24 exons and 23 introns with classical intron-exon junctions spanning more than 100 kbp. The importance of the HSD17B4 protein is stressed by the identification of patients with severe clinical abnormalities due to mutations in the HSD17B4 gene. We have now checked the consequences of one frequent mutation, G16 S, which results in inactivation of the enzyme due to loss of interaction with NAD+.

Structure of the gene for the human 17beta-hydroxysteroid dehydrogenase type IV

The 17beta-hydroxysteroid dehydrogenase type IV (17beta-HSD IV) is a multifunctional enzyme that is localized in the peroxisomes. The N-terminal part has dehydrogenase activity, the central part has hydratase activity, and the carboxy-terminal part is responsible for sterol transport. Recent observations of mutations in the human 17beta-HSD IV cDNA leading to a severe peroxisomal disorder motivated us to define the genomic organization of this gene mapped to Chromosome (Chr) 5q2. We show here that this gene consist of 24 exons and 23 introns with classical intron-exon junctions spanning more than 100 kbp. By mapping the regulatory region of this gene, we have shown that the first 400 bp upstream of the transcription start site are sufficient to activate transcription. The data presented here will permit sequence analysis of patients with peroxisomal disorders.