The identification and characterization of two promoters and the complete genomic sequence for the Wiskott-Aldrich syndrome gene

The Wiskott-Aldrich syndrome (WAS) is an X-linked disorder characterized by immunodeficiency, eczema and thrombocytopenia. The gene responsible for WA S was identified through positional cloning, and the function of the encode d protein (WASP) is still the subject of much speculation WASP is currently thought to be involved in the regulation of actin polymerization in hemato poietic cells. To study the elements that regulate the WASP gene, we have i dentified the sites for transcription initiation. We found that two promote rs were responsible for controlling WASP expression. Multiple transcription initiation sites were found immediately adjacent to the translation start site, however an alternate exon with a second promoter region was identifie d 6 kb upstream. Examination of the 5' sequence adjacent to the initiation sites in both promoters failed to reveal a TATA or CCAAT box, but numerous putative transcription factor binding sites including Sp1, Ets, c-Myb and P U.1 were apparent. Reporter constructs generated from each promoter showed functional activity in the Jurkat T-cell and HEL erythro-megakaryocytic cel l lines. Although the alternate exon sequence was extremely GC rich and con tained several potential binding elements, the primary promoter was stronge r than the upstream promoter in the cell lines assayed. The transcription f actor binding site profiles within each promoter suggested that they may pl ay different roles in regulating WASP expression depending on the stage of differentiation and development, and the cell lineage. in this study we hav e also reported the complete nucleotide sequence of the coding and interven ing sequences for the WASP gene. A comprehensive knowledge of the genomic s tructure and the further characterization of WASP gene expression will faci litate the continued investigation of mutations in WAS patients, and the ev entual prospect of gene therapy. (C) 1999 Academic Press.