Blouin R, Swierenga S H, Marceau N
Centre de recherche en cancérologie, Université Laval, L'Hôtel-Dieu de Québec, Canada.
Biochem Cell Biol. 1992 Jan;70(1):1-9. doi: 10.1139/o92-001.
T51B, a cell line of the rat liver nonparenchymal cell compartment, contains a cytokeratin (CK) pair composed of CK8, a CK typical of simple epithelium, and CK14, a CK usually present in proliferative stratified epithelium. T51B-Ni, a subclone selected by prolonged exposure of the parental clone to nickel subsulfide contains CK8 and CK18 (its usual partner in simple epithelium), as well as CK14, at a lower level. The two clones have comparable levels of vimentin. Northern blot analyses of cytoplasmic mRNA demonstrated that the differences in the steady state mRNA levels of each CK paralleled those observed at the protein level, thus showing that the regulatory events occurred prior to translation. The most prominent difference was a 30-fold higher level of CK18 mRNA in T51B-Ni cells. Run-off assays of isolated nuclei revealed that the level of CK8, CK14, and vimentin was regulated primarily at the transcriptional level. However, the large increase in CK18 mRNA levels in T51B-Ni cells did not result from a corresponding increase in the relative level of CK18 gene transcription nor from a change in cytoplasmic CK18 mRNA stability. Comparative Northern blot analyses of nuclear and cytoplasmic mRNAs further suggested that the control of CK18 gene expression in T51B cells is post-transcriptionally mediated by nuclear events.
T51B是大鼠肝非实质细胞区室的一种细胞系，含有由细胞角蛋白（CK）8和CK14组成的一对细胞角蛋白，CK8是单层上皮典型的细胞角蛋白，CK14通常存在于增殖性复层上皮中。T51B-Ni是通过将亲代克隆长时间暴露于硫化镍而筛选出的一个亚克隆，它含有CK8和CK18（其在单层上皮中的常见配对），以及含量较低的CK14。这两个克隆的波形蛋白水平相当。对细胞质mRNA的Northern印迹分析表明，每种细胞角蛋白的稳态mRNA水平差异与在蛋白质水平观察到的差异相似，从而表明调控事件发生在翻译之前。最显著的差异是T51B-Ni细胞中CK18 mRNA水平高出30倍。对分离细胞核的进行连续分析显示，CK8、CK14和波形蛋白的水平主要在转录水平受到调控。然而，T51B-Ni细胞中CK18 mRNA水平的大幅增加并非源于CK18基因转录相对水平的相应增加，也不是由于细胞质CK18 mRNA稳定性的改变。对细胞核和细胞质mRNA的比较Northern印迹分析进一步表明，T51B细胞中CK18基因表达的调控是由核事件在转录后介导的。
