Negative regulation of human insulin gene expression by the 5'-flanking region in non-pancreatic cells

We have examined the effect of the 5'-flanking region of the human insulin gene on its expression in non-pancreatic cells. The presence of the region containing the insulin gene enhancer (-339 to -169 bp) markedly repressed the promoter activity of the insulin gene. This suppressive phenomenon was restored by the addition of forskolin or dibutyryl cAMP, suggesting that this region alone is not sufficient to repress completely insulin gene expression in the presence of extracellular stimuli which increase the intracellular cAMP level. The hypervariable region (HVR) located at -365 bp also repressed the promoter activity. These results show negative regulation of human insulin gene expression in non-pancreatic cells by these regions.     

Specific expression of pfkfb4 gene in spermatogonia germ cells and analysis of its 5'-flanking region

The results presented demonstrate the expression of pfkfb4 gene in adult testis and in a mouse spermatogonia germ cell line (GC-1spg). The genomic organization of the human pfkfb4 gene shows the existence of 14 exons and 13 introns, spanning 45 kb. A detailed analysis of the 5'-flanking region by transient transfection assays with different 5'-deletion promoter constructs in GC-1spg and mouse sertoli cells (TM-4), allows us to define the minimal promoter unit, containing several GC-rich and ETF sequences along the first -141 nucleotides involved in basal expression. This gene is activated by serum and chemical hypoxia (CoCl(2) treatment) whereas beta-estradiol decreases its expression.     

Polymorphism in the 5'-flanking region of the human insulin gene and the incidence of diabetes.

DNA length polymorphism in the 5'-flanking region of the human insulin gene has been reported by Bell et al. (1981), Rotwein et al. (1981), and Owerbach and Nerup (1982). Bgl I digestions of human DNA that have been hybridized to an insulin probe using the Southern technique shows that there are two distinct groups of 5'-flanking lengths: one being shorter than 3.6 kilobases (kb) and the other being longer than 4.3 kb. The insulin genes with the former length are denoted as A1, and those with the latter as A2. Using these data and demographic data of diabetes, it is estimated that, when the fitness of A1 A2 individual was taken as unity, the amounts of fitness reduction for A1 A1 was 6.5 X 10(-6) and that for A2 A2 was -5.6 X 10(-6). Because of these small magnitudes of selection, the changes in population incidences of insulin-dependent diabetes and noninsulin-dependent diabetes are not affected much by the polymorphism in the 5'-flanking region of the insulin gene.