Chang H W, Li J, Vogt P K
Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, California 92037, USA.
Oncogene. 1996 Jul 18;13(2):441-4.
The qin oncogene is a cell-derived insert in the genome of avian sarcoma virus 31 (ASV 31) and functions as the oncogenic determinant of that virus. Overexpression of the viral and cellular versions of the Qin protein (v-Qin and c-Qin) induces oncogenic transformation of chicken embryo fibroblasts (CEF); v-Qin also rapidly induces fibrosarcomas in chickens. Qin proteins can bind to specific DNA sequences and act as transcriptional repressors. In this study, mutants of Qin were constructed in order to determine the molecular domains required for transformation of chicken embryo fibroblasts. Our data indicate that three regions required for transforming activity are located (i) between residues 74-141 at the amino terminus, (ii) in the winged helix domain and (iii) between residues 383-395 at the carboxyl terminus. A Qin mutant with 12 amino acids deleted from the carboxyl terminus (383-395) showed transforming activity that was lower than that of wild type Qin for CEF. Compare to wild type Qin transformants, the mutant transformed cells had a reduced ability for multilayered and for anchorage independent growth. Deletion of 48 amino acids from the carboxyl terminus of the Qin protein (347-395) completely abolished transforming activity. In contrast, deletion of 74 amino acids from the amino terminus did not affect transformation of CEF. However, further deletion of 68 amino acids (74-141) reduced but did not abolish transforming activity. Finally, deletion in the winged helix domain (218-295) completely abrogated oncogenic capacity in CEF. These results suggest that DNA binding and transcriptional repression may be important in Qin-induced oncogenic transformation.
秦癌基因是禽肉瘤病毒31（ASV 31）基因组中的一个细胞衍生插入片段，作为该病毒的致癌决定因素发挥作用。秦蛋白的病毒版本和细胞版本（v-Qin和c-Qin）的过表达会诱导鸡胚成纤维细胞（CEF）发生致癌转化；v-Qin还能在鸡体内迅速诱导纤维肉瘤。秦蛋白可与特定DNA序列结合并作为转录抑制因子发挥作用。在本研究中，构建了秦蛋白的突变体，以确定鸡胚成纤维细胞转化所需的分子结构域。我们的数据表明，转化活性所需的三个区域位于：（i）氨基末端的74-141位氨基酸之间，（ii）翼状螺旋结构域，以及（iii）羧基末端的383-395位氨基酸之间。从羧基末端（383-395）缺失12个氨基酸的秦突变体对CEF的转化活性低于野生型秦蛋白。与野生型秦转化细胞相比，该突变体转化的细胞形成多层结构和非锚定依赖性生长的能力降低。从秦蛋白羧基末端（347-395）缺失48个氨基酸完全消除了转化活性。相反，从氨基末端缺失74个氨基酸并不影响CEF的转化。然而，进一步缺失68个氨基酸（74-141）会降低但不会消除转化活性。最后，翼状螺旋结构域（218-295）的缺失完全消除了CEF中的致癌能力。这些结果表明，DNA结合和转录抑制在秦诱导的致癌转化中可能很重要。
