The human PEX3 gene encoding a peroxisomal assembly protein: Genomic organization, positional mapping, and mutation analysis in candidate phenotypes

In yeasts, the peroxin Pex3p was identified as a peroxisomal integral membr ane protein that presumably plays a role in the early steps of peroxisomal assembly. In humans, defects of peroxins cause peroxisomal biogenesis disor ders such as Zellweger syndrome. We previously reported data on the human P EX3 cDNA and its protein, which in addition to the peroxisomal targeting se quence contains a putative endoplasmic reticulum targeting signal. Here we report the genomic organization, sequencing of the putative promoter region , chromosomal localization, and physical mapping of the human PEX3 gene. Th e gene is composed of 12 exons and 11 introns spanning a region of approxim ately 40 kb. The highly conserved putative promoter region is very GC rich, lacks typical TATA and CCAAT boxes, and contains potential Sp1, AP1, and A P2 binding sites. The gene was localized to chromosome 6q23-24 and D6S279 w as identified to be the closest positional marker. As yeast mutants deficie nt in PEX3 have been shown to lack peroxisomes as well as any peroxisomal r emnant structures, human PEX3 is a candidate gene for peroxisomal assembly disorders. Mutation analysis of the human PEX3 gene was therefore performed in fibroblasts from patients suffering from peroxisome biogenesis disorder s. Complementation groups 1, 4, 7, 8, and 9 according to the numbering syst em of Kennedy Krieger Institute were analyzed but no difference to the wild -type sequence was detected. PEX3 mutations were therefore excluded as the molecular basis of the peroxisomal defect in these complementation groups. (C) 2000 Academic Press.