SCFbeta-TRCP controls oncogenic transformation and neural differentiation through REST degradation.

Howard Hughes Medical Institute, Department of Genetics, Harvard Partners Center for Genetics and Genomics, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, Massachusetts 02115, USA.
Nature (Impact Factor: 42.35). 04/2008; 452(7185):370-4. DOI: 10.1038/nature06780
Source: PubMed

ABSTRACT The RE1-silencing transcription factor (REST, also known as NRSF) is a master repressor of neuronal gene expression and neuronal programmes in non-neuronal lineages. Recently, REST was identified as a human tumour suppressor in epithelial tissues, suggesting that its regulation may have important physiological and pathological consequences. However, the pathways controlling REST have yet to be elucidated. Here we show that REST is regulated by ubiquitin-mediated proteolysis, and use an RNA interference (RNAi) screen to identify a Skp1-Cul1-F-box protein complex containing the F-box protein beta-TRCP (SCF(beta-TRCP)) as an E3 ubiquitin ligase responsible for REST degradation. beta-TRCP binds and ubiquitinates REST and controls its stability through a conserved phospho-degron. During neural differentiation, REST is degraded in a beta-TRCP-dependent manner. beta-TRCP is required for proper neural differentiation only in the presence of REST, indicating that beta-TRCP facilitates this process through degradation of REST. Conversely, failure to degrade REST attenuates differentiation. Furthermore, we find that beta-TRCP overexpression, which is common in human epithelial cancers, causes oncogenic transformation of human mammary epithelial cells and that this pathogenic function requires REST degradation. Thus, REST is a key target in beta-TRCP-driven transformation and the beta-TRCP-REST axis is a new regulatory pathway controlling neurogenesis.

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    ABSTRACT: The RE1 Silencing Transcription Factor (REST) acts as a governor of the mature neuronal phenotype by repressing a large consortium of neuronal genes in non-neuronal cells. In the developing nervous system, REST is present in progenitors and downregulated at terminal differentiation to promote acquisition of mature neuronal phenotypes. Paradoxically, REST is still detected in some regions of the adult nervous system, but how REST levels are regulated, and whether REST can still repress neuronal genes, is not known. Here, we report that homeostatic levels of REST are maintained in mature peripheral neurons by a constitutive post-transcriptional mechanism. Specifically, using a three-hybrid genetic screen, we identify the RNA binding protein, ZFP36L2, associated previously only with female fertility and hematopoiesis, and show that it regulates REST mRNA stability. Dorsal root ganglia in Zfp36l2 knock-out mice, or wild-type ganglia expressing ZFP36L2 shRNA, show higher steady-state levels of Rest mRNA and protein, and extend thin and disintegrating axons. This phenotype is due, at least in part, to abnormally elevated REST levels in the ganglia because the axonal phenotype is attenuated by acute knockdown of REST in Zfp36l2 KO DRG explants. The higher REST levels result in lower levels of target genes, indicating that REST can still fine-tune gene expression through repression. Thus, REST levels are titrated in mature peripheral neurons, in part through a ZFP36L2-mediated post-transcriptional mechanism, with consequences for axonal integrity. Copyright © 2014 the authors 0270-6474/14/3416650-12$15.00/0.
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