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

The goal of this study was to identify accessible chromatin peaks in lamina-associated domains of senescent cells. To establish senescence we used ionizing radiation (IR), overexpression of miR-340-5p, and knockdown of Lamin B Receptor (LBR).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: ATAC-sequencing of WI-38 fbroblasts to identify accessible chromatin in various cellular senescence models: PDL20 WI-38 fibroblasts were transfected with a control miRNA (N=2), precursor miRNA mimic of miR-340-5p (N=2), a siRNA to Lamin B Receptor (LBR, N=2), or exposure to ionizing radiation (10 Gy, siLBr, N=2), and cultured for 4 days before harvest for RNA extraction and RNA sequencing. Cells exposed to IR were cultured for an additional 10 days after expsoure.