TRANSCRIPTIONAL REGULATION OF THE HUMAN GLUT4 GENE PROMOTER IN DIABETIC TRANSGENIC MICE

We previously reported that 2400 base pairs (bp) of 5'-flanking DNA is sufficient for tissue-specific and hormonal/metabolic regulation of the human GLUT4 gene in transgenic mice (Liu, M.-L., Olson, A, L., Moye-Rowley, W. S., Buse, J. B., Bell, G. I., and Pessin, J. E. (1992) J. Biol, Chem, 267, 11673-11676), To further define the DNA sequences required for GLUT4 expression, we generated transgenic mice carrying 1975, 1639, 1154, 730, and 412 bp of the GLUT4 5'-flank (hG4) fused to the chloramphenicol acetyltransferase (CAT) reporter gene, The 1975-hG4-CAT, 1639-hG4-CAT, and 1154-hG4-CAT constructs were expressed in a tissue specific manner identical to the endogenous murine GLUT4 mRNA. Regulation of these reporter gene constructs in insulin-deficient diabetes also paralleled the endogenous gene, In contrast, 730-hG4-CAT was expressed at high levels only in skeletal muscle and at low levels in all of the other tissues examined, Additionally, expression of 412-hG4-CAT was completely unrestricted, Neither the 730-hG4-CAT nor the 412-hG4-CAT reporter genes displayed any insulin-dependent regulation, These data demonstrate that a skeletal muscle-specific DNA element is located within 730 bp of the GLUT4 5'-flanking DNA but that 1154 bp is necessary to direct the full extent of tissue-specific and insulin-dependent regulation of the human GLUT4 gene in transgenic mice.