miR-30e controls DNA damage-induced stress responses by modulating expression of the CDK inhibitor p21WAF1/CIP1 and caspase-3

Abstract

MicroRNAs (miRNAs), a class of small non-coding RNAs that usually cause gene silencing by translational repression or degradation of mRNAs, are implicated in DNA damage-induced stress responses. To identify senescence-associated miRNAs, we performed microarray analyses using wild-type and p53-deficient HCT116 colon carcinoma cells that following gamma-irradiation (γIR) are driven into senescence and apoptosis, respectively. Several miRNAs including miR-30e were found upregulated in a p53-dependent manner specifically in senescent cells, but not in apoptotic cells. Overexpression of miR-30e in HCT116 cells not only inhibited γIR-, etoposide- or miR-34a-induced caspase-3-like DEVDase activities and cell death, but greatly accelerated and augmented their senescent phenotype. Consistently, procaspase-3 protein, but not mRNA decreased in the presence of miR-30e, whereas expression of the cyclin-dependent kinase inhibitor p21 increased both at the mRNA and protein level. Performing luciferase reporter gene assays, we identified the 3′-UTR of the caspase-3 mRNA as a direct miR-30e target. In contrast, although miR-30e was unable to bind to the p21 mRNA, it increased expression of a luciferase construct containing the p21 promoter, suggesting that the miR-30e-mediated upregulation of p21 occurs indirectly at the transcriptional level. Interestingly, despite suppressing procaspase-3 expression, miR-30e was unable to protect RKO colon carcinoma cells from DNA damage-induced death or to induce senescence, as miR-30e completely fails to upregulate p21 in these cells. These data suggest that miR-30e functions in a cell type-dependent manner as an important molecular switch for DNA damage-induced stress responses and may thus represent a target of therapeutic value.

P53‐induced miR‐30e‐5p inhibits colorectal cancer invasion and metastasis by targeting ITGA6 and ITGB1

“…showed miR‐30e and miR‐30c to be upregulated in gamma‐irradiated senescent P53 wild‐type CRC cells but not in P53‐deficient cells. Their results were consistent with our findings, but interestingly they found none of the other miR‐30 family members (miR‐30a, −30 b, −30d) to be deregulated …”

“…Moreover, we also observed a significant decrease in cell proliferation in vitro , which was also mirrored in vivo where we observed significant decreases in tumor weight in the miR‐30e‐5p treated groups as compared to the corresponding controls. The decrease in proliferation was likely mediated by the activation of the cell cycle checkpoint regulators, P21 and P27, the up regulation of P21 by P53‐dependent expression of miR‐30e also having been reported by Sohn and colleagues . A rather interesting observation from our study was that both miR‐30e‐5p ‐mediated inhibition of proliferation and that of metastasis in vivo also occurred in P53 null cells signifying that miR‐30e‐5p is able to exert its tumor suppressive effects even in the absence of P53.…”

“…The decrease in proliferation was likely mediated by the activation of the cell cycle checkpoint regulators, P21 and P27, the up regulation of P21 by P53-dependent expression of miR-30e also having been reported by Sohn and colleagues. 32 A rather interesting observation from our study was that both miR-30e-5p -mediated inhibition of proliferation and that of metastasis in vivo also occurred in P53 null cells signifying that miR-30e-5p is able to exert its tumor suppressive effects even in the absence of P53.…”

“…Their results were consistent with our findings, but interestingly they found none of the other miR-30 family members (miR-30a, 230 b, 230d) to be deregulated. 32 A systemic analysis of potential putative targets identified integrin alpha-6 (ITGA6) and integrin beta-1 (ITGB1) as novel prime targets of miR-30e-5p and as molecules able to regulate steps of the metastasis cascade. ITGB1 (also known as CD29), is predominantly expressed in tumor cells and its overexpression has been observed in several cancer types.…”

The DEAD-box RNA helicase DDX41 is a novel repressor of p21WAF1/CIP1 mRNA translation

“…At the transcriptional level, p21 is mainly regulated by the tumor suppressor p53, particularly following DNA damage. However, the p21 promoter also contains response elements for several other transcription factors that are able to regulate p21 expression in response to a variety of stimuli in a p53-independent manner (12,13). Finally, p21 expression is also controlled posttranscriptionally at the mRNA level by numerous noncoding microRNAs and RNA-binding proteins (RBPs) that preferentially, but not exclusively, target sequences in the 3ЈUTR of the p21 mRNA (14 -16).…”