Regulation of expression by promoters versus internal ribosome entry site in the 5'-untranslated sequence of the human cyclin-dependent kinase inhibitor p27kip1.
Regulation of expression by promoters versus internal ribosome entry site in the 5'-untranslated sequence of the human cyclin-dependent kinase inhibitor p27kip1.
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DOI：
10.1093/nar/gki680
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发表时间：
2005
影响因子：
14.9
通讯作者：
Zhang JT
中科院分区：
文献类型：
--
作者：
Liu Z;Dong Z;Han B;Yang Y;Liu Y;Zhang JT
p27kip1 通过结合并抑制细胞周期蛋白依赖性激酶的活性来调节细胞增殖，其表达随细胞周期而波动。最近，使用传统双顺反子 DNA 测定的研究表明，p27kip1 的表达受到内部核糖体进入位点 (IRES) 介导的翻译起始的调节，并且一些 RNA 结合蛋白因子被认为在这种调节中发挥了一定作用。考虑到双顺反子 DNA 测定不可避免的缺点，可能会误导启动子活性或选择性剪接至 IRES，如之前所证明的，我们决定重新分析 p27kip1 的 5'-非翻译区 (5'-UTR) 序列，并使用更严格的方法（例如双顺反子 RNA 和无启动子双顺反子和单顺反子 DNA 测定）测试其是否包含 IRES 元件或启动子。我们发现人p27kip1的5'-UTR序列不具有任何显着的IRES活性。先前观察到的 IRES 活性可能是由 p27kip1 5'-UTR 序列中存在的启动子活性产生的。本研究结果表明转录调控可能在p27kip1表达中发挥重要作用，RNA结合因子调控p27表达的机制需要重新审视。这项研究的结果还进一步强调了需要更严格的研究（例如无启动子双顺反子和单顺反子 DNA 以及双顺反子 RNA 测试）的重要性，以保障未来细胞 IRES 的任何主张。
p27kip1 regulates cell proliferation by binding to and inhibiting the activity of cyclin-dependent kinases and its expression oscillates with cell cycle. Recently, it has been suggested from studies using the traditional dicistronic DNA assay that the expression of p27kip1 is regulated by internal ribosome entry site (IRES)-mediated translation initiation, and several RNA-binding protein factors were thought to play some role in this regulation. Considering the inevitable drawbacks of the dicistronic DNA assay, which could mislead a promoter activity or alternative splicing to IRES as previously demonstrated, we decided to reanalyze the 5′-untranslated region (5′-UTR) sequence of p27kip1 and test whether it contains an IRES element or a promoter using more stringent methods, such as dicistronic RNA and promoterless dicistronic and monocistronic DNA assays. We found that the 5′-UTR sequence of human p27kip1 does not have any significant IRES activity. The previously observed IRES activities are likely generated from the promoter activities present in the 5′-UTR sequences of p27kip1. The findings in this study indicate that transcriptional regulation likely plays an important role in p27kip1 expression, and the mechanism of regulation of p27 expression by RNA-binding factors needs to be re-examined. The findings in this study also further enforce the importance that more stringent studies, such as promoterless dicistronic and monocistronic DNA and dicistronic RNA tests, are required to safeguard any future claims of cellular IRES.
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