Abstract
DNA methyltransferase 1 (DNMT1) is a major epigenetic regulator associated with many biological processes. However, the roles and mechanisms of DNMT1 in skin aging are incompletely understood. Here we explored the role of DNMT1 in human skin fibroblasts senescence and its related regulatory mechanisms. DNMT1 expression decreased in passage-aged fibroblasts and DNMT1 silencing in young fibroblasts induced the senescence phenotype. MiR-217 is predicted to target DNMT1 mRNA and miR-217 expression increased in passage-aged fibroblasts. MiR-217 directly targeted the 3′-untranslated region (3′-UTR) of DNMT1 in HEK 293T cells and inhibited DNMT1 expression in fibroblasts. MiR-217 overexpression induced a senescence phenotype in young fibroblasts, and miR-217 downregulation in old HSFs partially reversed the senescence phenotype. However, these effects could be significantly rescued by regulating DNMT1 expression in fibroblasts. After regulating miR-217 levels, we analyzed changes in the promoter methylation levels of 24 senescent-associated genes, finding that 6 genes were significantly altered, and verified p16 and phosphorylated retinoblastoma (pRb) protein levels. Finally, an inverse correlation between DNMT1 and miR-217 expression was observed in skin tissues and different-aged fibroblasts. Together, these findings revealed that miR-217 promotes fibroblasts senescence by suppressing DNMT1-mediated methylation of p16 and pRb by targeting the DNMT1 3′-UTR.
Highlights
Aging is a phenomenon that is associated with a gradual decline in biological functions
We evaluated DNA methyltransferase 1 (DNMT1) expression in 10 patient-matched pairs of human skin fibroblasts (HSFs) that had undergone different numbers of passages by western blot analysis, finding that DNMT1 protein expression in passage-aged HSFs was markedly lower in HSFs from patients in the younger cohort (Figure 1A)
These data demonstrated that DNMT1 knockdown induced an erupted senescent phenotype in HSFs and that DNMT1 could play an important role in skin aging
Summary
Aging is a phenomenon that is associated with a gradual decline in biological functions. Cellular senescence of human skin fibroblasts (HSFs) has been proposed to be major underlying cause of skin aging [1]. DNA methyltransferase 1 (DNMT1), the major enzyme responsible for maintaining DNA methylation patterns, is located at the replication fork and methylates newly biosynthesized DNA to induce gene silencing [3, 4]. The expression of DNMT1 decreased gradually in both premature and replicative senescent human embryonic lung fibroblasts www.impactjournals.com/oncotarget [7], and DNMT1 knockdown caused telomere shortening in glioma cell lines [8]. Several studies have demonstrated a correlation between DNMT1 and the classical senescencerelated gene p16 in some cancer cells [9,10,11]
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