RESUMO
The role of the RNA-binding protein human antigen R (HuR) in hepatocarcinogenesis is still elusive. By employing short hairpin (sh)RNA-dependent knockdown approach, we demonstrate that lymphotoxin α (LTα) is a target of posttranscriptional gene regulation by HuR in hepatocellular carcinoma (HepG2) cells. Consequently, the increased mRNA decay upon HuR depletion significantly affects lymphotoxin expression at both, the mRNA and protein level. Biotin-pulldown assay showed that HuR specifically interacts with the 3'-untranslated region (3'-UTR) of the LTα mRNA. Furthermore, electrophoretic mobility shift assay (EMSA) implicates that the RNA-binding critically depends on the RNA recognition motif 2 (RRM2) and the hinge region of HuR.
Assuntos
Proteínas ELAV/fisiologia , Regulação da Expressão Gênica , Linfotoxina-alfa/genética , Processamento Pós-Transcricional do RNA , Regiões 3' não Traduzidas , Proteínas ELAV/genética , Ensaio de Desvio de Mobilidade Eletroforética , Técnicas de Silenciamento de Genes , Células Hep G2 , Humanos , Linfotoxina-alfa/metabolismo , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo RealRESUMO
A disintegrin and metalloproteinase 17 (ADAM17) is a metalloprotease that is overexpressed in many cancer types, including renal cancers. However, the regulatory mechanisms of ADAM17 in cancer development and progression are poorly understood. In the present work, we provide evidence using overexpression and inhibition of microRNA 145 (miR-145) that miR-145 negatively regulates ADAM17 expression. Furthermore, we show that ADAM17 negatively regulates miR-145 through tumor necrosis factor-α, resulting in a reciprocal negative feedback loop. In this study, the expression of ADAM17 and miR-145 correlated negatively in renal cancer tumor tissues and cell lines, suggesting an important regulatory mechanism. Additionally, we showed that the regulation of ADAM17 is partly involved in the effects of miR-145 on proliferation and migration, whereas no involvement in chemosensitivity was observed. Importantly, in the healthy kidney, miR-145 was detected in different cell types including tubular cells, which are considered the origin of renal cancer. In renal cancer cell lines, miR-145 expression was strongly suppressed by methylation. In summary, miR-145 is downregulated in renal cancer patients, which leads to the up-regulation of ADAM17 in renal cancer. Importantly, miR-145 and ADAM17 are regulated in a reciprocal negative feedback loop.