Hansji Herah, Leung Euphemia Y, Baguley Bruce C, Finlay Graeme J, Cameron-Smith David, Figueiredo Vandre C, Askarian-Amiri Marjan E
Auckland Cancer Society Research Centre, University of Auckland, 85 Park Rd, Grafton, Auckland, 1023, New Zealand.
Department of Molecular Medicine and Pathology, University of Auckland, 85 Park Rd, Grafton, Auckland, 1023, New Zealand.
Biol Direct. 2016 Nov 21;11(1):62. doi: 10.1186/s13062-016-0165-y.
Most of the eukaryotic genome is transcribed, yielding a complex network of transcripts including thousands of lncRNAs that generally lack protein coding potential. However, only a small percentage of these molecules has been functionally characterised, and discoveries of specific functions demonstrate layers of complexity. A large percentage of lncRNAs is located in the cytoplasm, associated with ribosomes but the function of the majority of these transcripts is unclear. The current study analyses putative mechanisms of action of the lncRNA species member ZFAS1 that was initially discovered by microarray analysis of murine tissues undergoing mammary gland development. As developmental genes are often deregulated in cancer, here we have studied its function in breast cancer cell lines.
Using human breast cancer cell lines, ZFAS1 was found to be expressed in all cell lines tested, albeit at different levels of abundance. Following subcellular fractionation, human ZFAS1 was found in both nucleus and cytoplasm (as is the mouse orthologue) in an isoform-independent manner. Sucrose gradients based on velocity sedimentation were utilised to separate the different components of total cell lysate, and surprisingly ZFAS1 was primarily co-localised with light polysomes. Further investigation into ribosome association through subunit dissociation studies showed that ZFAS1 was predominantly associated with the 40S small ribosomal subunit. The expression levels of ZFAS1 and of mRNAs encoding several ribosomal proteins that have roles in ribosome assembly, production and maturation were tightly correlated. ZFAS1 knockdown significantly reduced RPS6 phosphorylation.
A large number of lncRNAs associate with ribosomes but the function of the majority of these lncRNAs has not been elucidated. The association of the lncRNA ZFAS1 with a subpopulation of ribosomes and the correlation with expression of mRNAs for ribosomal proteins suggest a ribosome-interacting mechanism pertaining to their assembly or biosynthetic activity. ZFAS1 may represent a new class of lncRNAs which associates with ribosomes to regulate their function.
This article was reviewed by Christine Vande Velde, Nicola Aceto and Haruhiko Siomi.
大多数真核生物基因组都被转录，产生一个复杂的转录本网络，其中包括数千种通常缺乏蛋白质编码潜力的长链非编码RNA（lncRNA）。然而，这些分子中只有一小部分具有功能特征，特定功能的发现显示出其复杂性。很大一部分lncRNA位于细胞质中，与核糖体相关，但这些转录本中大多数的功能尚不清楚。当前的研究分析了lncRNA物种成员ZFAS1的假定作用机制，该成员最初是通过对经历乳腺发育的小鼠组织进行微阵列分析发现的。由于发育基因在癌症中经常失调，因此我们在此研究了它在乳腺癌细胞系中的功能。
使用人乳腺癌细胞系，发现ZFAS1在所有测试的细胞系中均有表达，尽管丰度水平不同。进行亚细胞分级分离后，发现人ZFAS1以不依赖于异构体的方式存在于细胞核和细胞质中（小鼠同源物也是如此）。利用基于速度沉降的蔗糖梯度来分离总细胞裂解物的不同成分，令人惊讶的是，ZFAS1主要与轻多核糖体共定位。通过亚基解离研究对核糖体结合进行的进一步研究表明，ZFAS1主要与40S小核糖体亚基相关。ZFAS1的表达水平与几种在核糖体组装、产生和成熟中起作用的核糖体蛋白编码mRNA的表达水平紧密相关。ZFAS1敲低显著降低了核糖体蛋白S6的磷酸化。
大量lncRNA与核糖体相关，但这些lncRNA中大多数的功能尚未阐明。lncRNA ZFAS1与核糖体亚群的结合以及与核糖体蛋白mRNA表达的相关性表明存在一种与其组装或生物合成活性相关的核糖体相互作用机制。ZFAS1可能代表一类新的与核糖体结合以调节其功能的lncRNA。
本文由克里斯汀·范德·维尔德、尼古拉·阿塞托和盐见治彦评审。
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