Regulation of phosphoenolpyruvate carboxykinase gene transcription by insulin and cAMP: reciprocal actions on initiation and elongation.
Regulation of phosphoenolpyruvate carboxykinase gene transcription by insulin and cAMP: reciprocal actions on initiation and elongation.
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胰岛素和 cAMP 对磷酸烯醇丙酮酸羧激酶基因转录的调节：起始和延伸的相互作用。
DOI：
10.1073/pnas.85.9.2954
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发表时间：
1988
影响因子：
11.1
通讯作者：
Granner,DK
中科院分区：
文献类型：
--
作者：
Sasaki,K;Granner,DK
从 H4IIE 大鼠肝癌细胞中分离的细胞核用于体外连续测定，探针针对磷酸烯醇丙酮酸羧激酶 [GTP：草酰乙酸羧基裂解酶（转磷酸化）； EC 4.1.1.32]基因，以分析转录是否在该基因上均匀地进行以响应胰岛素和cAMP治疗。与 cAMP 处理的细胞相比，胰岛素处理后与磷酸烯醇丙酮酸羧激酶基因相关的聚合酶 II 复合物较少，但它们分布均匀，因此胰岛素不会在离散位点阻断转录，也不会导致逐渐但渐进的过早终止。磷酸烯醇丙酮酸羧激酶初级转录物在cAMP处理的细胞中以约2500个核苷酸/分钟的速率合成，在胰岛素处理的细胞中以约1000个核苷酸/分钟的速率合成。因此，与 cAMP 相比，胰岛素延迟了转录物延伸，但这种作用并不能解释胰岛素对转录的总体影响。胰岛素治疗后，很少有新生转录物与该基因的前 69 个核苷酸相关，而在 cAMP 处理的细胞中，情况恰恰相反。这些观察结果使我们认为胰岛素和 cAMP 都直接在转录起始水平发挥其主要作用，但方式相反。
Nuclei isolated from H4IIE rat hepatoma cells were used in an in vitro run-on assay, with probes directed against various regions of the phosphoenolpyruvate carboxykinase [GTP: oxaloacetate carboxy-lyase (transphosphorylating); EC 4.1.1.32] gene, to analyze whether transcription proceeds uniformly across this gene in response to insulin and cAMP treatment. Fewer polymerase II complexes were associated with the phosphoenolpyruvate carboxykinase gene after insulin treatment, as compared with cAMP-treated cells, but they were distributed uniformly, so insulin does not block transcription at a discrete site, nor does it cause gradual, but progressive, premature termination. The phosphoenolpyruvate carboxykinase primary transcript was synthesized at a rate of about 2500 nucleotides per min in cAMP-treated cells and about 1000 nucleotides per min in insulin-treated cells. Thus insulin retards transcript elongation in comparison with cAMP, but this action does not account for the total effect insulin has on transcription. After insulin treatment, few, if any, nascent transcripts are associated with the first 69 nucleotides of the gene, whereas in cAMP-treated cells the opposite is true. These observations lead us to suggest that both insulin and cAMP exert their primary effects directly at the level of transcription initiation, but in opposite ways.