We will also OICR-9429 nmr connect the indirect crosstalk

between epigenetic regulators through miRNA mediation. Epigenetic mechanisms of miRNA dysregulation in cancer With the progress in DNA methylation detection techniques, numerous miRNAs have been identified that are modulated by DNA methylation, shedding light on the epigenetically regulated miRNAs. Among them, miR-9, miR-148, miR-124, miR-137, miR-34, miR-127 and miR-512 reportedly can be silenced by CpG hypermethylation in at least three types of cancers [6]. However, it is AZD2281 cell line still largely unknown which miRNAs can be altered owing to histone modifications. To date, histone methylation and histone deacetylation were confirmed to be involved in miRNA regulation. Understanding which

and how miRNAs are regulated by histone modifying effectors in cancer might be helpful in tumor treatment. MiR-29 The miR-29 family, which targets DNA methyltransferase 3 (DNMT3), is the first reported epi-miRNA, and is also the most extensively studied miRNA that is regulated by histone modification [9]. Recent studies show that transcription factors can regulate miRNA expression through epigenetic mechanisms. For instance, MYC can induce epigenetic regulation of miR-29 repression through histone deacetylation and tri-methylation in B-cell lymphomas (BCL), since it can recruit histone deacetylase 3 (HDAC3) and enhancer MG132 of zeste homolog 2 (EZH2) to the miR-29 promoter, forming a MYC/HDAC3/EZH2 co-repressor complex. Without MYC, however, the lack of binding of HDAC3 and EZH2 to the miR-29 promoter results AZD8931 datasheet in increased miR-29 expression [10]. Therefore, MYC plays an indispensable role in the epigenetic repression of miR-29 by inducing histone deacetylation and histone tri-methylation. Meanwhile, EZH2 can also repress miR-494 to create a positive feedback loop, which in turn increases MYC abundance and then sustains miR-29 repression in BCL [10]. These properties indicate that different epigenetic modifications can

cooperatively regulate the same miRNA, whereas a specific epigenetic effector can regulate more than one miRNAs in the same type of tumor. Previous research evidence suggested that the transcription factor Yin and yang 1 (YY-1) can recruit various proteins such as EZH2 and HDACs to target genes during various epigenetic events [11–13]. Later Wang et al. confirmed that nuclear factor κB (NF-κB) up-regulated YY-1 resulted in the recruitment of EZH2 and HDAC1 to the miR-29 promoter in myoblasts, leading to the down-regulation of miR-29 and maintaining cells in an undifferentiated state. Once myogenesis starts, the repressive complex containing YY-1/EZH2/HDAC will be replaced by an activating complex. Therefore, miR-29 is restored and in turn targets YY1 to ensure differentiation.