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Ute Schepers, Thorsten Lemm, Volker Herzog, Konrad Sandhoff
Characterization of Regulatory Elements in the 5'-Flanking Region of the GM2 Activator Gene
Lysosomal degradation of the ganglioside GM2 by human ?hexosaminidase A requires the presence of the GM2 activator protein as an essential cofactor. Here we demonstrate that GM2 activator mRNA is differentially expressed and mainly localized to the apical part of the epithelial cells of distal renal tubules and the collecting duct. In order to understand the mechanism underlying the regulation of the GM2 activator gene, we analyzed the genomic organization upstream exon 2 as well as the 5'flanking region. The GM2 activator gene spans about 16.8 kb with a first intron of 6.5 kb, and the transcription start is located at position -96 upstream from the ATG. DNA elements responsible for GM2 activator expression were identified in a PCRbased method of longdistance DNA walking. Sequence analysis revealed a 2.9 kb region upstream of the ATG that contained regulatory elements like CAAT boxes, Sp1 binding sites as well as AP1, and AP2 sites. Transfection experiments in COS-1 cells with a series of chimeras of 5'stepwise deletion mutants of the GM2 activator gene 5'flanking region and the secretory alkaline phosphatase (SEAP)reporter gene indicated that a genomic fragment encompassing 323 to +1bp had significant promoter activity. EMSA experiments showed that Sp1 and other transcription factors like AP1, AP2 and CCAATBox binding proteins are involved in GM2 activator gene regulation.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 381, 08/2000
Pages: 531 - 544