Reversible inhibition of a thyroid-specific trans-acting factor by Ras.
Reversible inhibition of a thyroid-specific trans-acting factor by Ras.
复制标题
Ras 对甲状腺特异性反式作用因子的可逆抑制。
DOI：
10.1101/gad.5.1.22
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发表时间：
1991
影响因子：
10.5
通讯作者：
Gottesman,ME
中科院分区：
文献类型：
--
作者：
Avvedimento,VE;Musti,AM;Ueffing,M;Obici,S;Gallo,A;Sanchez,M;DeBrasi,D;Gottesman,ME
将大鼠甲状腺细胞暴露于柯尔斯滕小鼠肉瘤病毒(KiMSV)的温度敏感变种RAS中1周，可使甲状腺球蛋白启动子(PTG)失活。细胞去分化与甲状腺特异性反式作用因子TgTF1的丢失平行，TgTF1与PTG结合。当RAS在39℃下变性时，TgTF1结合和PTG功能迅速恢复，没有合成新的蛋白质。在体外，用蛋白激酶A处理核提取液可使TgTF1重新激活，暴露于癌基因4周后，RAS的变性不再恢复TgTF1结合或重新激活PTG。同样，核提取物与蛋白激酶A孵育也不能重新激活TgTF1。然而，长期暴露于RAS的细胞在5-氮胞苷处理后确实产生了分化的克隆。我们认为RAS通过两个连续的步骤诱导去分化：(1)RAS降低PKA活性；TgTF1(或辅助蛋白)被去磷酸化，与PTG的结合被取消。(2)RAS的作用是通过甲基化，可能是TgTF1基因的甲基化。
Exposure of rat thyroid cells for 1 week to a temperature-sensitive variant of Kirsten murine sarcoma virus (KiMSV) Ras inactivated the thyroglobulin promoter (pTg). Cellular dedifferentiation was paralleled by the loss of the thyroid-specific trans-acting factor, TgTF1, which binds to pTg. When Ras was denatured by shifting cells to 39 degrees C, TgTF1 binding and pTg function recovered rapidly without the synthesis of new protein. TgTF1 could be reactivated in vitro by treating nuclear extracts with protein kinase A. After 4 weeks of exposure to the oncogene, denaturation of Ras no longer restored TgTF1 binding or reactivated pTg. Incubation of nuclear extracts with protein kinase A likewise did not reactivate TgTF1. Cells chronically exposed to Ras did, however, yield differentiated clones after treatment with 5-azacytidine. We suggest that Ras induces dedifferentiation in two sequential steps: (1) Ras reduces PKA activity; TgTF1 (or an auxiliary protein) becomes dephosphorylated, and binding to pTg is abolished. (2) The effects of Ras become imprinted by methylation, possibly of the TgTF1 gene.