Suppression of LBR by miR-340 disrupts chromatin, promotes cell senescence, and enhances senolysis (RNA-Seq 2)

One of the cellular processes influenced by microRNAs is senescence, a state of indefinite growth arrest triggered by sublethal cell damage. Here, through bioinformatic analysis and experimental validation, we identified miR-340-5p as a novel miRNA that foments cellular senescence. miR340-5p was highly abundant in diverse senescence models, and miR-340-5p overexpression in proliferating cells rendered them senescent. Among the target mRNAs, miR-340-5p prominently reduced the levels of LBR mRNA, encoding Lamin B Receptor (LBR). Loss of LBR by ectopic overexpression of miR-340-5p derepressed heterochromatin in lamina-associated domains (LADs), promoting the expression of DNA repetitive elements characteristic of senescence. Importantly, overexpressing miR-340-5p enhanced cellular sensitivity to senolytic compounds, while antagonization of miR-340-5p reduced senescent-cell markers and engendered resistance to senolytic-induced cell death. We propose that miR-340-5p can be exploited for clearing senescent cells to restore tissue homeostasis and mitigate damage by senescent cells in aging human pathologies. Overall design: WI-38 fibroblasts (PDL 20) were transfected either with control miRNA or a precursor miRNA mimic of miR-340-5p, and cultured for four days before RNA extraction and sequencing.微小RNA（microRNAs）调控的细胞过程之一为细胞衰老（senescence）——后者是一类由亚致死性细胞损伤诱导的无期限生长停滞状态。本研究通过生物信息学分析与实验验证，鉴定出miR-340-5p是一种可促发细胞衰老的新型微小RNA。miR-340-5p在多种衰老模型中均呈高表达水平；在增殖期细胞中过表达miR-340-5p可诱导这些细胞进入衰老状态。在其靶向的信使RNA（messenger RNA，mRNA）中，miR-340-5p可显著下调LBR mRNA的表达水平，该基因编码核纤层蛋白B受体（Lamin B Receptor，LBR）。通过异位过表达miR-340-5p造成的LBR缺失，可解除核纤层关联结构域（lamina-associated domains，LADs）内异染色质的抑制状态，进而促进衰老特征性DNA重复序列的表达。尤为重要的是，过表达miR-340-5p可增强细胞对衰老清除剂的敏感性；而拮抗miR-340-5p则可降低衰老细胞标志物的表达水平，并使细胞获得对衰老清除剂诱导死亡的抵抗能力。本研究提出，可利用miR-340-5p清除衰老细胞，以恢复组织稳态，并减轻衰老细胞在人类衰老相关病理过程中造成的组织损伤。实验整体设计：将处于第20代群体倍增水平（PDL 20）的WI-38成纤维细胞，分别转染对照微小RNA或miR-340-5p的前体微小RNA模拟物，培养四天后进行RNA提取与测序。