Cross-Regulation between an Alternative Splicing Activator and a Transcription Repressor Controls Neurogenesis

Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Toronto, Ontario M5S 3E1, Canada.
Molecular cell (Impact Factor: 14.02). 09/2011; 43(5):843-50. DOI: 10.1016/j.molcel.2011.08.014
Source: PubMed


Neurogenesis requires the concerted action of numerous genes that are regulated at multiple levels. However, how different layers of gene regulation are coordinated to promote neurogenesis is not well understood. We show that the neural-specific Ser/Arg repeat-related protein of 100 kDa (nSR100/SRRM4) negatively regulates REST (NRSF), a transcriptional repressor of genes required for neurogenesis. nSR100 directly promotes alternative splicing of REST transcripts to produce a REST isoform (REST4) with greatly reduced repressive activity, thereby activating expression of REST targets in neural cells. Conversely, REST directly represses nSR100 in nonneural cells to prevent the activation of neural-specific splicing events. Consistent with a critical role for nSR100 in the inhibition of REST activity, blocking nSR100 expression in the developing mouse brain impairs neurogenesis. Our results thus reveal a fundamental role for direct regulatory interactions between a splicing activator and transcription repressor in the control of the multilayered regulatory programs required for neurogenesis.

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Available from: Noel J Buckley, Oct 20, 2015
    • "Generation of N2A cell lines expressing nSR100/SRRM4-or GFP-targeting shRNAs, and the 293T cell line with inducible Flag-nSR100 expression, have been previously described (Calarco et al., 2009; Raj et al., 2011). To establish inducible Flag-nSR100 N2A cell lines, the full-length mouse nSR100 open reading frame (ORF) with an N-terminal 3xFlag tag was cloned into a PiggyBac vector (gift from Dr. Andras Nagy, Lunenfeld-Tanenbaum Research Institute). "
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    ABSTRACT: The vertebrate and neural-specific Ser/Arg (SR)-related protein nSR100/SRRM4 regulates an extensive program of alternative splicing with critical roles in nervous system development. However, the mechanism by which nSR100 controls its target exons is poorly understood. We demonstrate that nSR100-dependent neural exons are associated with a unique configuration of intronic cis-elements that promote rapid switch-like regulation during neurogenesis. A key feature of this configuration is the insertion of specialized intronic enhancers between polypyrimidine tracts and acceptor sites that bind nSR100 to potently activate exon inclusion in neural cells while weakening 3' splice site recognition and contributing to exon skipping in nonneural cells. nSR100 further operates by forming multiple interactions with early spliceosome components bound proximal to 3' splice sites. These multifaceted interactions achieve dominance over neural exon silencing mediated by the splicing regulator PTBP1. The results thus illuminate a widespread mechanism by which a critical neural exon network is activated during neurogenesis.
    Molecular Cell 09/2014; 56(1). DOI:10.1016/j.molcel.2014.08.011 · 14.02 Impact Factor
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    • "Although these observations highlight the importance of combinatorial regulation in splicing, nothing is known about how multiple splicing factors act together to shape splicing networks at single neuron resolution. Characterization of individual target transcripts within splicing networks have identified important splicing events that contribute to specific neuronal phenotypes (Aoto et al., 2013; Raj et al., 2011; Yano et al., 2010). However, the difficulty of systematic network interrogation in vertebrate models has made it challenging to perform functional analyses of substantial numbers of targets within splicing regulatory networks in vivo. "
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    ABSTRACT: Alternative splicing is important for the development and function of the nervous system, but little is known about the differences in alternative splicing between distinct types of neurons. Furthermore, the factors that control cell-type-specific splicing and the physiological roles of these alternative isoforms are unclear. By monitoring alternative splicing at single-cell resolution in Caenorhabditis elegans, we demonstrate that splicing patterns in different neurons are often distinct and highly regulated. We identify two conserved RNA-binding proteins, UNC-75/CELF and EXC-7/Hu/ELAV, which regulate overlapping networks of splicing events in GABAergic and cholinergic neurons. We use the UNC-75 exon network to discover regulators of synaptic transmission and to identify unique roles for isoforms of UNC-64/Syntaxin, a protein required for synaptic vesicle fusion. Our results indicate that combinatorial regulation of alternative splicing in distinct neurons provides a mechanism to specialize metazoan nervous systems.
    Molecular Cell 06/2014; DOI:10.1016/j.molcel.2014.05.004 · 14.02 Impact Factor
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    • "Interestingly, in several cancer types REST transcripts undergo frequent and complex AS,105 and in lung cancer this is regulated by the neuronal splice factor SRRM4.106 In neuronal cells, REST and SRRM4 form a regulatory feedback loop107 and it will be interesting to explore the interplay between these proteins in PCa. Since NEPC is extremely aggressive with survival of <1 year,101 it will be important to explore the functional role of AS in NEPC, the mechanisms of its regulation and the role of REST transcriptional complex in NEPC biology (Figure 3). "
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    ABSTRACT: Alternative splicing (AS) is a crucial step in gene expression. It is subject to intricate regulation, and its deregulation in cancer can lead to a wide array of neoplastic phenotypes. A large body of evidence implicates splice isoforms in most if not all hallmarks of cancer, including growth, apoptosis, invasion and metastasis, angiogenesis, and metabolism. AS has important clinical implications since it can be manipulated therapeutically to treat cancer and represents a mechanism of resistance to therapy. In prostate cancer (PCa) AS also plays a prominent role and this review will summarize the current knowledge of alternatively spliced genes with important functional consequences. We will highlight accumulating evidence on AS of the components of the two critical pathways in PCa: androgen receptor (AR) and phosphoinositide 3-kinase (PI3K). These observations together with data on dysregulation of splice factors in PCa suggest that AR and PI3K pathways may be interconnected with previously unappreciated splicing regulatory networks. In addition, we will discuss several lines of evidence implicating splicing regulation in the development of the castration resistance.
    Asian Journal of Andrology 05/2014; 16(4). DOI:10.4103/1008-682X.127825 · 2.60 Impact Factor
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