Liu M L, Olson A L, Moye-Rowley W S, Buse J B, Bell G I, Pessin J E
Department of Physiology and Biophysics, University of Iowa, Iowa City 52242.
J Biol Chem. 1992 Jun 15;267(17):11673-6.
To study the molecular basis of tissue-specific expression of the GLUT4/muscle-fat facilitative glucose transporter gene, we generated lines of transgenic mice carrying 2.4 kilobases of the 5'-flanking region of the human GLUT4 gene fused to a chloramphenicol acetyltransferase (CAT) reporter gene (hGLUT4[2.4]-CAT). This reporter gene construct was specifically expressed in tissues that normally express GLUT4 mRNA, which include both brown and white adipose tissues as well as cardiac, skeletal, and smooth muscle. In contrast, CAT reporter activity was not detected in brain or liver, two tissues that do not express the GLUT4 gene. In addition, the relative levels of CAT mRNA driven by the human GLUT4 promoter in various tissues of these transgenic animals mirrored those of the endogenous mouse GLUT4 mRNA. Since previous studies have observed alterations in GLUT4 mRNA levels induced by fasting and refeeding (Sivitz, W. I., DeSautel, S. L., Kayano, T., Bell, G. I., and Pessin, J. E. (1989) Nature 340, 72-74), the regulated expression the hGLUT4[2.4]-CAT transgene was also assessed in these animals. Fasting was observed to decrease CAT activity in white adipose tissue which was super-induced upon refeeding. These alterations in CAT expression occurred in parallel to the changes in endogenous mouse GLUT4 mRNA levels. Although CAT expression in skeletal muscle and brown adipose tissue was unaffected, the endogenous mouse GLUT4 mRNA was also refractory to the effects of fasting/refeeding in these tissues. These data demonstrate that 2.4 kilobases of the 5'-flanking region of the human GLUT4 gene contain all the necessary sequence elements to confer tissue-specific expression and at least some of the sequence elements controlling the hormonal/metabolic regulation of this gene.
为了研究GLUT4/肌肉-脂肪易化型葡萄糖转运蛋白基因组织特异性表达的分子基础，我们构建了携带与人氯霉素乙酰转移酶（CAT）报告基因融合的人GLUT4基因5'侧翼区2.4千碱基片段的转基因小鼠品系（hGLUT4[2.4]-CAT）。该报告基因构建体在正常表达GLUT4 mRNA的组织中特异性表达，这些组织包括棕色和白色脂肪组织以及心脏、骨骼肌和平滑肌。相反，在不表达GLUT4基因的脑和肝这两种组织中未检测到CAT报告基因活性。此外，这些转基因动物不同组织中由人GLUT4启动子驱动的CAT mRNA相对水平与内源性小鼠GLUT4 mRNA的水平一致。由于先前的研究观察到禁食和再喂食可诱导GLUT4 mRNA水平的变化（西维茨，W. I.，德索泰尔，S. L.，卡亚诺，T.，贝尔，G. I.，和佩辛，J. E.（1989年）《自然》340，72 - 74），因此也在这些动物中评估了hGLUT4[2.4]-CAT转基因的调控表达。观察到禁食会降低白色脂肪组织中的CAT活性，而再喂食会使其超诱导。CAT表达的这些变化与内源性小鼠GLUT4 mRNA水平的变化平行。尽管骨骼肌和棕色脂肪组织中的CAT表达未受影响，但这些组织中的内源性小鼠GLUT4 mRNA对禁食/再喂食的影响也不敏感。这些数据表明，人GLUT4基因5'侧翼区的2.4千碱基片段包含赋予组织特异性表达所需的所有序列元件以及至少一些控制该基因激素/代谢调控的序列元件。
