A mechanism of differential expression of GLUT2 in hepatocyte and pancreatic beta-cell line.
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 beta-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 beta-cell derived cell line. When -585/-146 construct was expressed in liver, the activity was decreased to 46%, whereas the activity in beta-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 beta-cell specifically expresses the UPE binding protein. Assuming that there may be Box VI-binding protein playing negative roles both in hepatocyte and beta-cell, and that the protein acts as a negative regulator of GLUT2 gene, the UPE binding protein in the beta-cell may overcome the inhibition by binding to the protein.
Kim
J W
JW
Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, Seoul, Korea.
Kim
Y K
YK
Ahn
Y H
YH
D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D018983:DNA Footprinting; D003850:Deoxyribonuclease I; D005786:Gene Expression Regulation; D051273:Glucose Transporter Type 2; D007515:Islets of Langerhans / Q000166:cytology / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051381:Rats; D018808:Transcription Factor AP-1
D051273:Glucose Transporter Type 2; D009004:Monosaccharide Transport Proteins; D018808:Transcription Factor AP-1; D003850:Deoxyribonuclease I