| Budget Amount *help |
¥6,800,000 (Direct Cost: ¥6,800,000)
Fiscal Year 1994: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1993: ¥5,000,000 (Direct Cost: ¥5,000,000)
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| Research Abstract |
We previously isolated human gastirc inhibitory polypeptide (GIP) gene, liver type glucose transporter (GLUT2) gene and somatostatin receptor (SSTR2) gene. The expression of these genes are regulated by concentration of glucose, but the mechanisms are unknown. In this study, we isolated the 5'-promoter regions of human GIP gene, human GLUT2 gene and mouse SSTR2 gene and generated various deletion mutants. After cloned into chloramphenicol acetyl-transferase (CAT) reporter plasmid or luciferase reporter plasmid, these deletion mutants were transfected to HIT-T15 cells, and the promoter activities were assayd. In case of human GIP gene, tow cyclic-AMP respnse elements (CRE) are located upstream of the transcription initiation site and sequences between -180 and +14 are essential to its promoter activity. Furthermore, calcium supplement increases the human GIP promoter activity via two CREs and this phenomenon is augmented by high glucose concentration. As to human GLUT2 gene, deletion analysis shows that sequences downstream of the transcription initiation site (+126-+308) are indispensable for the basal promoter activity and the sequences between +29 and +308 contributed to glucose induced transcription enhancement. Similar phenomenon is cbserved in primary cultured rat hepatocytes. We performed PCR-SSCP analysis to detect the mutation in these glucose responsive sequences of the human GLUT2 gene in diabetic polulation, but no mutation was found in diabetics studied. We also examined the promoter activity of the mouse SSTR2 gene 5'-flanking region. Transient expression studies showed no significant glucose-induced augmentation of the promoter activity, but deletion analyzes revealed two possible transcription initiation sites.
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