Tikoo A, Czekay S, Viars C, White S, Heath J K, Arden K, Maruta H
Ludwig Institute for Cancer Research, P.O. Box 2008, Royal Melbourne Hospital, Parkville, 3050, Melbourne, Australia.
Gene. 2000 Oct 17;257(1):23-31. doi: 10.1016/s0378-1119(00)00387-5.
To date, two distinct genes coding for Ras GAP-binding phosphoproteins of 190kDa, p190-A and p190-B, have been cloned from mammalian cells. Rat p190-A of 1513 amino acids shares 50% sequence identity with human p190-B of 1499 amino acids. We have previously demonstrated, using rat p190-A cDNA, that full-length p190-A is a tumor suppressor, reversing v-Ha-Ras-induced malignancy of NIH 3T3 cells through both the N-terminal GTPase (residues 1-251) and the C-terminal Rho GAP (residues 1168-1441) domains. Here we report the cloning of the full-length human p190-A cDNA and its first exon covering more than 80% of this protein, as well as its chromosomal mapping. Human p190-A encodes a protein of 1514 amino acids, and shares overall 97% sequence identity with rat p190-A. Like the p190-B exon, the first exon of p190-A is extremely large (3.7 kb in length), encoding both the GTPase and middle domains (residues 1-1228), but not the remaining GAP domain, suggesting a high conservation of genomic structure between two p190 genes. Using a well characterized monochromosome somatic cell hybrid panel, fluorescent in situ hybridization (FISH) and other complementary approaches, we have mapped the p190-A gene between the markers D19S241E and STD (500 kb region) of human chromosome 19q13.3. Interestingly, this chromosomal region is known to be rearranged in a variety of human solid tumors including pancreatic carcinomas and gliomas. Moreover, at least 40% glioblastoma/astrocytoma cases with breakpoints in this region were previously reported to show loss of the chromosomal region encompassing p190-A, suggesting the possibility that loss or mutations of this gene might be in part responsible for the development of these tumors.
迄今为止，已从哺乳动物细胞中克隆出两个编码190kDa Ras GAP结合磷蛋白的不同基因，即p190 - A和p190 - B。1513个氨基酸的大鼠p190 - A与1499个氨基酸的人p190 - B具有50%的序列同一性。我们之前使用大鼠p190 - A cDNA证明，全长p190 - A是一种肿瘤抑制因子，通过N端GTP酶（第1 - 251位氨基酸）和C端Rho GAP（第1168 - 1441位氨基酸）结构域逆转v - Ha - Ras诱导的NIH 3T3细胞恶性转化。在此，我们报告全长人p190 - A cDNA及其覆盖该蛋白80%以上的首个外显子的克隆，以及其染色体定位。人p190 - A编码一个1514个氨基酸的蛋白，与大鼠p190 - A总体上具有97%的序列同一性。与p190 - B外显子一样，p190 - A的首个外显子极大（长度为3.7kb），编码GTP酶和中间结构域（第1 - 1228位氨基酸），但不编码其余的GAP结构域，这表明两个p190基因之间基因组结构高度保守。使用特征明确的单染色体体细胞杂种板、荧光原位杂交（FISH）及其他互补方法，我们将p190 - A基因定位在人染色体19q13.3的标记D19S241E和STD之间（500kb区域）。有趣的是，已知该染色体区域在包括胰腺癌和神经胶质瘤在内的多种人类实体瘤中发生重排。此外，先前报道至少40%在该区域有断点的胶质母细胞瘤/星形细胞瘤病例显示包含p190 - A的染色体区域缺失，这表明该基因的缺失或突变可能在一定程度上导致这些肿瘤的发生。
