The level of expression of the rat growth hormone gene in liver tumor cells is at least eight orders of magnitude less than that in anterior pituitary cells
The level of expression of the rat growth hormone gene in liver tumor cells is at least eight orders of magnitude less than that in anterior pituitary cells
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肝肿瘤细胞中大鼠生长激素基因的表达水平比垂体前叶细胞至少低8个数量级
DOI：
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发表时间：
1983
影响因子：
5.3
通讯作者：
P. O’Farrell
中科院分区：
文献类型：
--
作者：
R. Ivarie;B. Schacter;P. O’Farrell
对表达肝脏特异性基因产物的大鼠肝肝癌细胞（HTC）进行了大鼠生长激素（rGH）基因的表达测定，该基因通常在垂体前叶生长激素细胞中表达。免疫沉淀和二维凝胶电泳的结合提供了一种高度灵敏的 rGH 合成检测，其水平低至细胞蛋白质合成的 10(9) 分之一（或每个细胞的 4 个 rGH 分子）。在此水平上未检测到 rGH 表达。基因组 DNA 的 Southern 杂交分析表明，HTC 细胞中表达的缺失并非源于 rGH 基因的缺失。由于该基因的表达量超过垂体前叶蛋白合成的 30%，因此两种细胞类型之间的分化调节 rGH 表达超过 10(8) 倍。此外，使用 DNA 过量溶液杂交来测量 rGH mRNA 序列的水平。开发了一种从重组质粒制备单链探针的新颖且通用的方法。检测灵敏度为 10(8) 分之一的杂交分析未能检测到 HTC 细胞细胞核或细胞质中的任何 rGH RNA 序列。因此，可以得出结论，肝肿瘤细胞中rGH表达的限制很可能发生在基因转录水平上，并且出于所有实际目的，rGH基因在肝癌细胞中被完全关闭。
Rat liver hepatoma cells (HTC) which express liver-specific gene products were assayed for the expression of the rat growth hormone (rGH) gene, which is normally expressed in anterior pituitary somatotrophs. The combination of immunoprecipitation and two-dimensional gel electrophoresis provided a highly sensitive assay for rGH synthesis at levels as low as one part in 10(9) of cell protein synthesis (or four molecules of rGH per cell). No rGH expression was detected at this level. The lack of expression in HTC cells did not derive from a deletion of the rGH gene, as shown by Southern hybridization analysis of genomic DNA. Because the gene is expressed at greater than 30% of anterior pituitary protein synthesis, differentiation regulated rGH expression by over 10(8)-fold between the two cell types. Additionally, DNA-excess solution hybridization was used to measure the level of rGH mRNA sequences. A novel and general method for preparing single-strand probes from recombinant plasmids was developed. Hybridization analyses with a sensitivity of detection of 1 part in 10(8) failed to detect any rGH RNA sequences in either the nucleus or cytoplasm of HTC cells. It is concluded, therefore, that the restriction in rGH expression in the liver tumor cells is likely to occur at the level of the transcription of the gene, and that for all practical purposes, the rGH gene is completely shut off in the hepatoma cells.