Cloning and characterization of the human tartrate-resistant acid phosphatase (TRAP) gene.

The expression and protein structure of the tartrate-resistant acid phosphatase (TRAP), an iron-containing lysosomal glycoprotein in cells of the mononuclear phagocyte system, have been analyzed extensively in the past. In some diseases, like hairy cell leukemia and Gaucher's disease, cytochemically detected TRAP expression is used as a disease-associated marker. In this paper we describe the isolation of a genomic cosmid clone of the human TRAP gene. Restriction mapping revealed a 22-kb insert and the complete genomic structure of the TRAP gene. A 6-kb HindIII-fragment harboring the entire TRAP gene was subcloned and the 5'-flanking region of 3026 bp was sequenced. Analysis of the sequence data showed the presence of potential transcription factor binding sites. Two transcriptional start sites were identified in the untranslated exon 1 at positions -349 and -347 bp relative to the translational start codon. Linked to a luciferase-encoding reporter gene the 5'-flanking region was sufficient to direct transcription in the heterologous cell line BHK-21. Treatment of the transfected cells with different modulators of the intracellular iron content showed that regulation of TRAP expression is dependent on iron. In summary, these data imply a possible functional role of the TRAP gene product either in the storage or the transport of iron.