Molecular mechanism of transcriptional regulation of pyruvate kinase gene by glucose and insulin

1.SHARP2不参与l型丙酮酸激酶（LPK）基因的碳水化合物反应性，但在肝细胞中，胰岛素通过磷酸肌苷3激酶途径刺激其转录。结合LII和LII'的NF1家族蛋白和结合LI的HNF1α协同刺激肝脏中LPK基因的转录。NF1通过其DNA结合域直接与HNF1α的激活域相互作用，从而刺激HNF1α的DNA结合活性。一种不直接影响LPK基因启动子活性的同源域蛋白Hex通过其同源域与pw -同源域相互作用来刺激HNF1α活性。因此，Hex通过HNF1α.4刺激LPK基因的转录。这表明ChREBP本身参与了胰岛素/葡萄糖对ChREBP基因的转录调控。分离大鼠ChREBP基因，对其5′侧长约1000bp的区域进行测序。在上游区域发现了与LPK基因碳水化合物响应元件相似的区域，但该区域对碳水化合物不响应。此外，我们还发现该基因在上游区域含有应答CREBP的序列。胰岛素在转录和转录后水平调控m2型PK的表达。胰岛素应答元件被认为存在于PKM基因上游-0.5 kb至-2.2kb区域。

1.SHARP2 was not involved in carbohydrate responsiveness of the L-type pyruvate kinase(LPK) gene, but its transcription was stimulated by insulin through phosphoinositide 3-kinase pathway in hepatocytes.2.The LPK gene transcription in the liver was synergistically stimulated by NF1 family proteins bound to LII and LII', and HNF1α bound to LI. NF1 directly interacted with activation domain of HNF1α via its DNA binding domain, which resulted in stimulation of DNA binding activity of HNF1α.3.A homeodomain protein Hex, which did not affect any activity of the LPK gene promoter directly, stimulated HNF1α activity by interacting with POU-homeodomain via its homeodomain. Thus, Hex stimulated transcription of the LPK gene through HNF1α.4.It was suggested that ChREBP itself is involved in transcriptional regulation of the ChREBP gene by insulin/glucose. The rat ChREBP gene was isolated and its 5'-flanking region up to about 1000 bp was sequenced. The region similar to carbohydrate response element of the LPK gene was found in the upstream region, but it was not responsive to carbohydrate. In addition, we found that the gene contained sequences responsive to CREBP in the upstrem region.5.Expression of the M2-type PK was regulated by insulin at both transcriptional and posttranscriptional levels. Insulin-responsive element was suggested to be present in the upstream region of the PKM gene from -0.5 kb to -2.2kb.