Pruikkonen Sofia, Kallio Marko J
Department of Physiology, Institute of Biomedicine, University of Turku, Turku 20520, Finland.
Centre for Biotechnology, University of Turku, Turku 20520, Finland.
Br J Cancer. 2017 May 23;116(11):1451-1461. doi: 10.1038/bjc.2017.110. Epub 2017 Apr 27.
Several microRNA (miRNA) molecules have emerged as important post-transcriptional regulators of tumour suppressor and oncogene expression. Ras association domain family member 1 (RASSF1) is a critical tumour suppressor that controls multiple aspects of cell proliferation such as cell cycle, cell division and apoptosis. The expression of RASSF1 is lost in a variety of cancers due to the promoter hypermethylation.
miR-193a-3p was identified as a RASSF1-targeting miRNA by a dual screening approach. In cultured human cancer cells, immunoblotting, qRT-PCR, luciferase reporter assays, time-lapse microscopy and immunofluorescence methods were used to study the effects of excess miR-193a-3p on RASSF1 expression and cell division.
Here, we report a new miRNA-mediated mechanism that regulates RASSF1 expression: miR-193a-3p binds directly to RASSF1-3'UTR and represses the mRNA and protein expression. In human cancer cells, excess of miR-193a-3p causes polyploidy through impairment of the Rassf1-Syntaxin 16 signalling pathway that is needed for completion of cytokinesis. In the next cell cycle the miR-193a-3p-overexpressing cells exhibit multipolar mitotic spindles, mitotic delay and elevated frequency of cell death.
Our results suggest that besides epigenetic regulation, altered expression of specific miRNAs may contribute to the loss of Rassf1 in cancer cells and cause cell division errors.
几种微小RNA（miRNA）分子已成为肿瘤抑制因子和癌基因表达的重要转录后调节因子。Ras关联结构域家族成员1（RASSF1）是一种关键的肿瘤抑制因子，可控制细胞增殖的多个方面，如细胞周期、细胞分裂和细胞凋亡。由于启动子高甲基化，RASSF1在多种癌症中表达缺失。
通过双重筛选方法鉴定出miR-193a-3p是靶向RASSF1的miRNA。在培养的人癌细胞中，采用免疫印迹、qRT-PCR、荧光素酶报告基因检测、延时显微镜和免疫荧光方法研究过量miR-193a-3p对RASSF1表达和细胞分裂的影响。
在此，我们报道了一种调节RASSF1表达的新的miRNA介导机制：miR-193a-3p直接与RASSF1-3'UTR结合并抑制mRNA和蛋白质表达。在人癌细胞中，过量的miR-193a-3p通过损害胞质分裂完成所需的Rassf1-Syntaxin 16信号通路导致多倍体形成。在下一个细胞周期中，过表达miR-193a-3p的细胞表现出多极有丝分裂纺锤体、有丝分裂延迟和细胞死亡频率升高。
我们的结果表明，除了表观遗传调控外，特定miRNA表达的改变可能导致癌细胞中Rassf1的缺失并引起细胞分裂错误。
