Codony C, Guil S, Caudevilla C, Serra D, Asins G, Graessmann A, Hegardt F G, Bach-Elias M
IIBB-CSIC (Instituto de Investigaciones Biomédicas de Barcelona-Consejo Superior de Investigaciones Científicas), Dept. PMT, Unidad de Biología y Farmacología Molecular del Cáncer, c/Jorge Girona Salgado 18-26, 08034 Barcelona, Spain.
Oncogene. 2001 Jun 21;20(28):3683-94. doi: 10.1038/sj.onc.1204473.
In man, activated N-, K- and H-ras oncogenes have been found in around 30% of the solid tumours tested. An exon known as IDX, which has been described previously and is located between exon 3 and exon 4A of the c-H-ras pre-mRNA, allows an alternative splicing process that results in the synthesis of the mRNA of a putative protein named p19. It has been suggested that this alternative pathway is less tumorigenic than that which results in the activation of p21. We have used the mammalian trans-splicing mechanism as a tool with which to modulate this particular pre-mRNA processing to produce mRNA similar to that of mature p19 RNA. The E4A exon of the activated H-ras gene was found to be a good target for external trans-splicing. We reprogrammed the rat carnitine octanoyltransferase exon 2 to specifically invade the terminal region of H-ras. Assays performed with this reprogrammed trans-exon showed that the trans-splicing product was obtained in competition with cis-splicing of the D intron of the H-ras gene, and was associated with concomitant down-modulation of D intron cis-splicing. We also found that the exon 4A of the human c-H-ras gene underwent successive trans-splicing rounds with an external exon.
在人类中，已在约30%的测试实体瘤中发现激活的N-、K-和H-ras癌基因。一个名为IDX的外显子，此前已有描述，位于c-H-ras前体mRNA的外显子3和外显子4A之间，它允许一种可变剪接过程，导致合成一种名为p19的假定蛋白质的mRNA。有人提出，这种可变途径的致瘤性低于导致p21激活的途径。我们利用哺乳动物的反式剪接机制作为一种工具，来调节这种特定的前体mRNA加工过程，以产生与成熟p19 RNA相似的mRNA。发现激活的H-ras基因的E4A外显子是外部反式剪接的良好靶点。我们对大鼠肉碱辛酰转移酶外显子2进行了重新编程，使其特异性地侵入H-ras的末端区域。用这种重新编程的反式外显子进行的实验表明，反式剪接产物是在与H-ras基因D内含子的顺式剪接竞争中获得的，并且与D内含子顺式剪接的同时下调有关。我们还发现，人类c-H-ras基因的外显子4A与一个外部外显子进行了连续的反式剪接轮次。
