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KMID : 0620919980300010015
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Experimental & Molecular Medicine
1998 Volume.30 No. 1 p.15 ~ p.20
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A Mechanism of differential expression of GLUT2 in hepatocyte and pancreatic β-cell line
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Yong Ho Ahn/Jae Woo Kim
Yu Kyong Kim/Yong Ho Ahn
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Abstract
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DNase I footprinting assay using liver nuclear extracts revealed six protected regions between nucleotide -600 and +110 and hence named Box I-VI. Upstream promoter element (UPE), a DNA element playing crucial role in transcriptional control of the tissue specific expression of pancreatic β-cell, has been detected within the proximal region of rat GLUT2 promoter. This region is included in Box VI. The protein-DNA interaction in this region (Box VI) was confirmed by mobility shift assay using liver nuclear extracts. Deletion of the region between -585 bp and -146 bp resulted in dramatic changes in promoter activity when they were expressed in liver and β-cell derived cell line. When -585/-146 construct was expressed in liver, the activity was decreased to 46%, whereas the activity in β-cell line, HIT-T15 cell, was increased by 84% when compared to -146/+190 construct. These opposing phenomena can be explained by the fact that β-cell specifically expresses the UPE binding protein. Assuming that there may be Box VI-binding protein playing negative roles both in hepatocyte and β-cell, and that the protein acts as a negative regulator of GLUT2 gene, the UPE binding protein in the β-cell may overcome the inhibition by binding to the protein.
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KEYWORD
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GLUT2 gene expression, hepatocyte, β-cell, upstream promoter element,
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