Project description:Metformin has been commonly used for decades to treat type 2 diabetes. Recent data indicates that mice treated with metformin live longer and healthier lives. Here, we show that chronic metformin exposure in mice and diabetics taking metformin have higher levels of the microRNA processing protein, Dicer. Examination of how metformin affects Dicer expression revealed that metformin alters binding of the AUF1 RNA-binding protein to DICER1 mRNA, which leads to stabilization of DICER1 mRNA. We found differential changes in microRNA expression in mice treated with metformin or caloric restriction, a proven life extending intervention. Several of these microRNAs are important for regulating cellular senescence and lifespan in model organisms. Consistent with this observation, treatment with metformin decreased cellular senescence in a Dicer-dependent manner. These data lead us to hypothesize that changes in Dicer levels may be important for organismal aging and that interventions that upregulate Dicer expression (e.g., metformin) may offer new therapeutic approaches to combat or prevent age-related diseases. Key words: diabetes mellitus, metformin, senescence, miRNA, RNA-binding proteins
Project description:The mammalian RNA-binding protein AUF1 (AU-binding factor 1, also known as heterogeneous nuclear ribonucleoprotein D, hnRNP D) binds to numerous mRNAs and influences their post-transcriptional fate. Given that many AUF1 target mRNAs encode muscle-specific factors, we investigated the function of AUF1 in skeletal muscle differentiation. In mouse C2C12 myocytes, where AUF1 levels rise at the onset of myogenesis and remain elevated throughout myocyte differentiation into myotubes, RIP (RNP immunoprecipitation) analysis indicated that AUF1 binds prominently to Mef2c (myocyte enhancer factor 2c) mRNA, which encodes the key myogenic transcription factor Mef2c. By performing mRNA half-life measurements and polysome distribution analysis, we found that AUF1 associated with the 3’UTR of Mef2c mRNA and promoted Mef2c translation without affecting Mef2c mRNA stability. In addition, AUF1 promoted Mef2c gene transcription via a lesser-known role of AUF1 in transcriptional regulation. Importantly, lowering AUF1 delayed myogenesis, while ectopically restoring Mef2c expression levels partially rescued the impairment of myogenesis seen after reducing AUF1 levels. We propose that Mef2c is a key effector of the myogenesis program promoted by AUF1. Keywords: ribonucleoprotein complex; post-transcriptional gene regulation; muscle cell differentiation; myocytes; mRNA translation; mRNA stability; post-transcriptional gene regulation; transcriptome
Project description:Although several studies indicate that ARE-specific RNA binding proteins (ARE-BPs) contribute to the development of cancer, the detailed functions and mechanisms of ARE-BPs have not been fully elucidated. By using a bioinformatics analysis of two well-established hepatocellular carcinoma (HCC) datasets, we identified the AU-rich binding factor 1(AUF1), one of the well-known ARE-BPs, was abnormally highly expressed in HCC and the high expression of AUF1 was correlated with poor prognosis of HCC patients. The prognostic value of AUF1 expression was also confirmed in our HBV-related HCC cohorts. Gain and loss of function analyses demonstrated that AUF1 promoted HCC tumorigenesis both in vitro and in vivo. Mechanistically, we found that aldoketo reductase family 1 member B 10(AKR1B10) was a critical target of AUF1 and was essential for sustaining the AUF1-induced proliferation of HCC cells. AUF1 stabilized AKR1B10 mRNA by binding to the 3'UTR region of AKR1B10. Additionally, we confirmed that E2F1 enhanced AUF1 expression in HCC through the transcription level, and in HBV-related HCC, HBx could up-regulate E2F1 expression and promote the expression of AUF1. Our study reveals a novel role of AUF1 in promoting hepatocarcinogenesis via the post-transcriptional regulation of AKR1B10 expression and proposes that the HBx/E2F1/AUF1/AKR1B10 pathway may serve as a potential therapeutic target in HCC.
