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Noncoding RNAs (ncRNAs) direct a remarkable number of diverse functions in development and disease through their regulation of transcription, RNA processing and translation. Leading the charge in the RNA revolution is a class of ncRNAs that are synthesized at active enhancers, called enhancer RNAs (eRNAs). Here, we review recent insights into the biogenesis of eRNAs and the mechanisms underlying their multifaceted functions and consider how these findings could inform future investigations into enhancer transcription and eRNA function.

The specific Sirt1 activator SRT1720 increases mitochondrial function in skeletal muscle, presumably by activating Sirt1. However, Sirt1 gain of function does not increase mitochondrial function, which raises a question about the central role of Sirt1 in SRT1720 action. Moreover, it is believed that the metabolic effects of SRT1720 occur independently of AMP-activated protein kinase (AMPK), an important metabolic regulator that increases mitochondrial function. Here, we show that SRT1720 activates AMPK in a Sirt1-independent manner and SRT1720 activates AMPK by inhibiting a cAMP degrading phosphodiesterase (PDE) in a competitive manner. Inhibiting the cAMP effector protein Epac prevents SRT1720 from activating AMPK or Sirt1 in myotubes. Moreover, SRT1720 does not increase mitochondrial function or improve glucose tolerance in AMPKα2 knockout mice. Interestingly, weight loss induced by SRT1720 is not sufficient to improve glucose tolerance. Therefore, contrary to current belief, the metabolic effects produced by SRT1720 require AMPK, which can be activated independently of Sirt1.

A study of the super-enhancer landscape in three mouse T-helper lymphocyte subsets identifies nodes that have key roles in cell identity, with the locus encoding Bach2, a key negative regulator of effector differentiation, emerging as the most prominent T-cell super-enhancer. Super-enhancer interaction with T cells Super-enhancers are a group of transcriptional factors specialized for the regulation of cellular functions related to cell identity and genetic disease risk. This study of the super-enhancer landscape in three mouse T-helper lymphocyte subsets identifies nodes that have crucial roles in cell identity, with the Bach2 locus, encoding the transcription factor BACH2, which is an important negative regulator of effector differentiation, emerging as the most prominent T-cell super-enhancer. Perturbation of Bach2 leads to a preferential effect on the expression of super-enhancer-associated genes and non-coding RNAs. This work demonstrates a systematic approach by which the super-enhancer map of relevant cell types can be integrated with human genetics to discover drug target genes. Enhancers regulate spatiotemporal gene expression and impart cell-specific transcriptional outputs that drive cell identity.sup.1. Super-enhancers (SEs), also known as stretch-enhancers, are a subset of enhancers especially important for genes associated with cell identity and genetic risk of disease.sup.2,3,4,5,6. CD4.sup.+ T cells are critical for host defence and autoimmunity. Here we analysed maps of mouse T-cell SEs as a non-biased means of identifying key regulatory nodes involved in cell specification. We found that cytokines and cytokine receptors were the dominant class of genes exhibiting SE architecture in T cells. Nonetheless, the locus encoding Bach2, a key negative regulator of effector differentiation, emerged as the most prominent T-cell SE, revealing a network in which SE-associated genes critical for T-cell biology are repressed by BACH2. Disease-associated single-nucleotide polymorphisms for immune-mediated disorders, including rheumatoid arthritis, were highly enriched for T-cell SEs versus typical enhancers or SEs in other cell lineages.sup.7. Intriguingly, treatment of T cells with the Janus kinase (JAK) inhibitor tofacitinib disproportionately altered the expression of rheumatoid arthritis risk genes with SE structures. Together, these results indicate that genes with SE architecture in T cells encompass a variety of cytokines and cytokine receptors but are controlled by a 'guardian' transcription factor, itself endowed with an SE. Thus, enumeration of SEs allows the unbiased determination of key regulatory nodes in T cells, which are preferentially modulated by pharmacological intervention., Author(s): Golnaz Vahedi [sup.1] , Yuka Kanno [sup.1] , Yasuko Furumoto [sup.2] , Kan Jiang [sup.1] , Stephen C. J. Parker [sup.3] [sup.7] , Michael R. Erdos [sup.3] , Sean [...]

Nuclear acetyltransferases promote and deacetylases inhibit skeletal muscle-gene expression, suggesting the potential effectiveness of deacetylase inhibitors (DIs) in modulating skeletal myogenesis. Surprisingly, previous studies have indicated that DIs suppress myogenesis. The recent observations that histone deacetylases associate with the muscle-regulatory proteins MyoD and MEF2C only in undifferentiated myoblasts prompted us to evaluate the effect of DIs at distinct stages of the myogenic program. We found that exposure of established rodent and human muscle cells to distinct DIs has stage-specific effects. Exposure of undifferentiated skeletal myoblasts to DIs, followed by incubation in differentiation medium, enhanced the expression of muscle-specific reporters and increased the levels of endogenous muscle proteins, leading to a dramatic increase in the formation of multinucleated myotubes. By contrast, simultaneous exposure of muscle cells to differentiation medium and DIs inhibited the myogenic program. Likewise, embryos exposed in utero to nonteratogenic doses of DI at the early stages of somitic myogenesis (embryonic day 8.5) exhibited an increased number of somites and augmented expression of a muscle-specific transgene as well as endogenous muscle genes. The functional effects induced by DIs were mirrored by changes in the state of acetylation of histones present at a muscle-gene enhancer and of MyoD itself. These results represent the first evidence that DIs can enhance muscle differentiation and suggest the rationale for their use in manipulating adult and embryonic skeletal myogenesis. deacetylase inhibitors | gene expression | MyoD | skeletal muscle differentiation | embryos

The regulation of the p300 and p300/CBP-associated factor (PCAF) histone acetyltransferases (HAT) was investigated. Results showed that the basic helix-loop-helix protein Twist directly binds two independent HAT domains and regulates the HAT activities of p300 and PCAF. It was also found that the N terminus of the Twist is the primary domain interacting with p300 and PCAF and that the effects of the Twist are imitated by the adenovirus E1A protein.

The transcriptional regulation of the human cardiac alpha-actin (HCA) promoter was analyzed in primary cultures of rat cardiomyocytes. The same DNA sequences are required for HCA expression in both skeletal and myocardial cells, including a basic helix-loop-helix (bHLH)-binding E box and binding sites for serum response factor (SRF) and Sp1. Cardiac nuclear factors corresponding to SRF and Sp1 interact with these sequences. Moreover, the element binding MyoD in skeletal muscle cells is bound by a related protein in cardiomyocytes. The results suggest that a member of the bHLH family, with SRF and Sp1, regulates myocardial expression of the cardiac alpha-actin gene.