Identification and characterization of a tissue-specific silencer element in the first intron of the human acid maltase gene.
Deficiency of acid maltase (acid alpha-glucosidase), a lysosomal enzyme that degrades glycogen, results in glycogenosis type II, an autosomal recessive disease whose manifestations and severity largely depend on the level of residual enzyme activity. Previous studies have established that there are transcriptional control elements in the first intron; in particular a silencer responsive to Hes-1 and YY1 has been identified in the human hepatoma line, HepG2. This region functions as an enhancer in human fibroblasts. Here we have localized a silencer active in fibroblasts to a nearby 25-bp element in intron 1. This element repressed thymidine kinase promoter activity by about 50% in both orientations in human fibroblasts. This silencer, as with the previous one, is tissue specific since constructs containing this region are inactive in HepG2 cells. Electrophoretic mobility shift assay revealed three proteins specifically binding to the element in fibroblasts, and site-directed mutagenesis analysis indicated that all the three proteins binding to the element contribute to the silencer function. The data may be helpful for designing therapy to increase the level of enzyme, particularly when, as in most adults with the disease, there is reduced production of structurally normal enzyme.
Yan
B
B
Arthritis and Rheumatism Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892-1820, USA.
Raben
N
N
Lu
N
N
Plotz
P H
PH
D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000378:metabolism; D020868:Gene Silencing; D005087:Glucan 1,4-alpha-Glucosidase / Q000235:genetics* / Q000378:metabolism; D006009:Glycogen Storage Disease Type II / Q000235:genetics*; D006801:Humans; D007438:Introns; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D017384:Sequence Deletion; D014162:Transfection; D014407:Tumor Cells, Cultured; D000520:alpha-Glucosidases
D017931:DNA Primers; D015500:Chloramphenicol O-Acetyltransferase; D000520:alpha-Glucosidases; D005087:Glucan 1,4-alpha-Glucosidase