Expression and regulation of the human and mouse aspartylglucosaminidase gene

Aspartylglucosaminidase (AGA) is a lysosomal enzyme that catalyzes one of the final steps in the degradation of N-linked glycoproteins. Here we have analyzed the tissue-specific expression and regulation of the human and mouse AGA genes. We isolated and characterized human and mouse AGA 5'-flanking sequences including the promoter regions. Primer extension assay revealed multiple transcription start sites in both genes, characteristic of a housekeeping gene. The cross-species comparison studies pinpointed an approximately 450-base pair (bp) homologous region in the distal promoter. In the functional analysis of human AGA 5' sequence, the critical promoter region was defined, and an additional upstream region of 181 bp exhibiting an inhibitory effect on transcription was identified. Footprinting and gel shift assays indicated protein binding to the core promoter region consisting of two Sp1 binding sites, which were sufficient to produce basal promoter activity in the functional studies. The results also suggested the binding of a previously uncharacterized transcription factor to a 23-bp stretch in the inhibitory region.