GENOMIC ORGANIZATION AND MOLECULAR CHARACTERIZATION OF A GENE ENCODING HSPXF, A HUMAN PEROXISOMAL FARNESYLATED PROTEIN

A protein modification essential for the cellular sorting of many biol ogically relevant proteins is the covalent attachment of prenyl lipids by specific transferases. Isoprenylation is known to render protein d omains hydrophobic, thereby facilitating the interaction with lipid bi layers and/or membrane proteins. The target for the modification with farnesyl groups is the COOH-terminal sequence CaaX. Among the variety of farnesylated proteins the only one reported so far to be located to peroxisomes is the 37-kDa peroxisomal farnesylated hamster protein Px F. Recently we published data on the cDNA of the human gene HK33 (A. B raun et at., 1994, Gene 146: 291-295), which was revealed to be the hu man ortholog of PxF and was consequently renamed HsPXF. The genomic st ructure, molecular characterization, and evolutionary conservation of HsPXF are described herein. The exact location of the gene was defined as chromosome 1q22. The gene spans a region of approximately 9 kb, co ntaining eight exons and seven introns. The 5' upstream region showed two potential Spl-binding sites and an Alu repetitive sequence. Lucife rase reporter activating capacity confirmed the presumed promoter acti vity of this region. On the transcriptional level, we detected four sp lice variants originating either from exon skipping or from alternativ e splicing events. For the HsPXF protein, a carboxyterminal farnesylat ion at cysteine residues was demonstrated. Through the use of HsPXF-sp ecific antibodies, the protein was shown to be attached to the outer s urface of peroxisomes. This localization together with the similarity to a peroxisomal assembly protein from Saccharomyces cerevisiae sugges ts HsPXF is involved in the process of peroxisomal biogenesis or assem bly. (C) 1997 Academic Press.