Department of Tumour Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.
Department of Core Facilities, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.
Sci Rep. 2017 Aug 28;7(1):9655. doi: 10.1038/s41598-017-10189-1.
The microRNAs in the miR-34 family, consisting of miR-34a, miR-34b and miR-34c, are tumour suppressors. The annotated human miR-34b-5p has one additional base at the 5' end of the common miR-34 family seed sequence, compared to miR-34a-5p and miR-34c-5p. This extra base results in a shift of the seed sequence, which would affect the target gene repertoire and have functional consequences. During our studies of miR-34 functions, we investigated the precise sequence of mature miR-34b-5p in human cells by deep sequencing. We found that a miR-34b-5p without the extra base was the predominant form in both non-malignant and malignant cells derived from several human tissues, indicating that the miR-34b annotation is misleading. We evaluated the functional implications of the seed shift, by comparing the effect of mimics representing the alternative miR-34b-5p sequences in MDA-MB-231 cells. In contrast to the annotated miR-34b, the endogenously expressed miR-34b displayed tumour suppressive characteristics in vitro similarly to miR-34c. These data demonstrate the importance of determining the precise sequence of a mature microRNA before exploring miRNA functions.
miR-34 家族中的 microRNAs，包括 miR-34a、miR-34b 和 miR-34c，都是肿瘤抑制因子。与 miR-34a-5p 和 miR-34c-5p 相比，注释的人 miR-34b-5p 在共同 miR-34 家族种子序列的 5'端有一个额外的碱基。这个额外的碱基导致种子序列发生移位，这将影响靶基因库，并产生功能后果。在我们对 miR-34 功能的研究中，我们通过深度测序研究了人细胞中成熟 miR-34b-5p 的精确序列。我们发现，在来自几种人体组织的非恶性和恶性细胞中，没有额外碱基的 miR-34b-5p 是主要形式，这表明 miR-34b 的注释是有误导性的。我们通过比较代表替代 miR-34b-5p 序列的模拟物在 MDA-MB-231 细胞中的作用，评估了种子移位的功能意义。与注释的 miR-34b 相比，内源性表达的 miR-34b 在体外显示出与 miR-34c 相似的肿瘤抑制特征。这些数据表明，在探索 miRNA 功能之前，确定成熟 microRNA 的精确序列是很重要的。
