Biomedical Sciences Research Institute, University of Ulster, Coleraine, Northern Ireland BT52 1SA, UK.
Mol Carcinog. 2010 Feb;49(2):190-9. doi: 10.1002/mc.20589.
CYP1B1 mRNA is expressed constitutively in all normal extrahepatic human tissues, though the protein is usually undetectable. In contrast, CYP1B1 protein is expressed at high levels in tumors. In this study CYP1B1 mRNA and protein expression was measured in a panel of cell lines indicating that CYP1B1 regulation is altered in tumor cell lines in vitro. Interrogation of ONCOMINE revealed that CYP1B1 mRNA is not significantly overexpressed in tumors compared to normal tissues, suggesting CYP1B1 is subject to posttranscriptional control. Analysis of the CYP1B1 mRNA revealed a complex 5' untranslated region (UTR) containing a small upstream open-reading frame (uORF). These features are present in mRNAs subject to translational control so the effect of the 5'UTR was tested using in vitro translation in CHO-K1 cells. The 5'UTR significantly inhibited luciferase reporter gene translation, and mutation of the uORF start codon abolished the inhibitory effect. The 5'UTR also interacted with the microRNA-27b recognition element in the CYP1B1 mRNA 3'UTR to almost completely inhibit translation. CYP1B1 is subject to a high degree of translational control, which may explain the absence of protein expression in normal cells. Alterations in translational control during malignant transformation may help to explain the tumor-specific expression of CYP1B1 protein.
CYP1B1mRNA 在所有正常的肝外人体组织中持续表达，尽管蛋白质通常无法检测到。相比之下，CYP1B1 蛋白在肿瘤中高水平表达。在这项研究中，我们测量了一系列细胞系中的 CYP1B1mRNA 和蛋白表达，表明 CYP1B1 调节在体外肿瘤细胞系中发生改变。ONCOMINE 的查询结果表明，与正常组织相比，肿瘤中 CYP1B1mRNA 没有明显过表达，这表明 CYP1B1 受到转录后控制。对 CYP1B1mRNA 的分析显示，其 5'非翻译区 (UTR) 包含一个小的上游开放阅读框 (uORF)。这些特征存在于受翻译控制的 mRNA 中，因此使用 CHO-K1 细胞中的体外翻译来测试 5'UTR 的影响。5'UTR 显著抑制了荧光素酶报告基因的翻译，而 uORF 起始密码子的突变则消除了抑制作用。5'UTR 还与 CYP1B1mRNA3'UTR 中的 microRNA-27b 识别元件相互作用，几乎完全抑制了翻译。CYP1B1 受到高度翻译控制，这可能解释了正常细胞中没有蛋白质表达的原因。恶性转化过程中翻译控制的改变可能有助于解释 CYP1B1 蛋白的肿瘤特异性表达。
