Lee, K. K. et al. Distinct functional domains in emerin bind lamin A and DNA-bridging protein BAF. J. Cell Sci. 114, 4567-4573

Department of Cell Biology, Johns Hopkins University School of Medicine, 725 N. Wolfe St., Baltimore, MD 21205, USA.
Journal of Cell Science (Impact Factor: 5.43). 01/2002; 114(Pt 24):4567-73.
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Loss of emerin, a lamin-binding nuclear membrane protein, causes Emery-Dreifuss muscular dystrophy. We analyzed 13 site-directed mutations, and four disease-causing mutations that do not disrupt emerin stability or localization. We show that emerin binds directly to barrier-to-autointegration factor (BAF), a DNA-bridging protein, and that this binding to BAF requires conserved residues in the LEM-motif of emerin. Emerin has two distinct functional domains: the LEM-domain at the N-terminus, which mediates binding to BAF, and a second functional domain in the central region, which mediates binding to lamin A. Disease mutation Delta95-99 mapped to the lamin-binding domain and disrupted lamin A binding in vitro. Two other disease-linked residues, Ser54 and Pro183, mapped outside the BAF and lamin-binding domains, suggesting that emerin may have additional functional domains relevant to disease. The disease-linked emerin proteins all remained active for binding to BAF, both in vitro and in vivo, suggesting that disease can result from the loss of specific molecular interactions between emerin and either lamin A or putative novel partner(s). The demonstration that emerin binds directly to BAF, coupled to similar results for LAP2, provides proof in principle that all LEM-domain nuclear proteins can interact with BAF, with interesting implications for chromatin attachment to the nuclear envelope.

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    • "Deletion 'DL' removed residues 1–47 (the LEM domain) as the negative control for binding to BAF. Deletion 'DM' removed 'middle' residues 67–108; this region is required to bind full-length lamin A in vitro (Lee et al., 2001 "
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    ABSTRACT: Emerin is a conserved nuclear membrane LEM-domain protein that binds lamins and BAF (barrier-to-integration factor; BANF1) as a component of nuclear lamina structure. We report an advance in understanding the molecular basis of emerin function: inter-molecular emerin-emerin association. Residues 170-220 were sufficient to bind other emerin molecules homotypically (via residues 170-220) or heterotypically in vitro. Deletion analysis showed residues 187-220 contain a positive element essential for intermolecular association in cells. Conversely, deletion of residues 168-186 inactivated a proposed negative element, required to limit or control association. GFP-emerin association with nuclear BAF in cells required the LEM-domain, and positive element. Emerin peptide arrays revealed direct binding of residues 170-220 to residues 206-225 (proposed positive element) and two 'heterotypic' partners: residues 147∼174 (particularly (153)PMYGRDSAYQSITHYRP(169)) and the LEM-domain. Emerin residues 1-132 and 159-220 ((159)SAYQSITHYRPVS(171) being important or essential)- were each sufficient to bind lamin A or B1 tails in vitro, identifying two independent regions of molecular contact with lamins. These results, and predicted emerin intrinsic disorder, support multiple 'backbone' and LEM-domain configurations of a proposed intermolecular emerin network at the nuclear envelope.
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    • "Emerin is a ubiquitously expressed integral membrane protein of the INM (Manilal et al., 1996) that interacts with nuclear proteins regulating chromatin structure and transcription. Studies in vitro showed that emerin binds preferentially Lamin A/C (Lee et al., 2001) and requires it for proper NE targetting (Sullivan et al., 1999). Lamin-associated polypeptide 2 (LAP2) is a family of six alternatively spliced isoforms . "
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    ABSTRACT: Lamin A/C is a structural protein of the nuclear envelope and cardiac involvement in Lamin A/C mutations was one of the first phenotypes to be reported in humans, suggesting a crucial role of this protein in the cardiomyocytes function. Mutations in LMNA gene cause a class of pathologies generically named ‘Lamanopathies’ mainly involving heart and skeletal muscles. Moreover, the well known disease called Hutchinson-Gilford Progeria Syndrome (HGPS) due to extensive mutations in LMNA gene, in addition to the systemic phenotype of premature aging, is characterized by the death of patients at around 13 typically for a heart attack or stroke, suggesting again the heart as the main site sensitive to Lamin A/C disfunction. Indeed, the identification of the roles of the Lamin A/C in cardiomyocytes function is a key area of exploration.One of the primary biological roles recently conferred to Lamin A/C is to affect contractile cells lineage determination and senescence. Then, in differentiated adult cardiomyocytes both the ‘structural’ and ‘gene expression hypothesis’ could explain the role of Lamin A in the function of cardiomyocytes. In fact, recent advances in the field propose that the structural weakness/stiffness of the NE, regulated by Lamin A/C amount in NE, can ‘consequently’ alter gene expression.This article is protected by copyright. All rights reserved
    Biology of the Cell 07/2014; 106(10). DOI:10.1111/boc.201400033 · 3.51 Impact Factor
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    • "Given that the absence of EMR-1 and/or LEM-2 allows the ‘EMR-1 only’ elements to interact more frequently with LMN-1, we hypothesize that EMR-1 and LEM-2 physically prevent LMN-1 from binding to these regions. It is known that human and mouse emerin interacts physically with transcription factors involved in muscle development, including β-catenin [23] and Lmo7 [24], and with chromatin associated factors, such as BAF and HDAC3 [13,48]. Similarly, the mammalian LEM-2-like protein MAN1 interacts with Smads at the NE to regulate transforming growth factor-β signaling [49]. "
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    ABSTRACT: Laminopathies are diseases characterized by defects in nuclear envelope structure. A well-known example is Emery-Dreifuss muscular dystrophy, which is caused by mutations in the human lamin A/C and emerin genes. While most nuclear envelope proteins are ubiquitously expressed, laminopathies often affect only a subset of tissues. The molecular mechanisms underlying these tissue-specific manifestations remain elusive. We hypothesize that different functional subclasses of genes might be differentially affected by defects in specific nuclear envelope components. Here we determine genome-wide DNA association profiles of two nuclear envelope components, lamin/LMN-1 and emerin/EMR-1 in adult Caenorhabditis elegans. Although both proteins bind to transcriptionally inactive regions of the genome, EMR-1 is enriched at genes involved in muscle and neuronal function. Deletion of either EMR-1 or LEM-2, another integral envelope protein, causes local changes in nuclear architecture as evidenced by altered association between DNA and LMN-1. Transcriptome analyses reveal that EMR-1 and LEM-2 are associated with gene repression, particularly of genes implicated in muscle and nervous system function. We demonstrate that emr-1, but not lem-2, mutants are sensitive to the cholinesterase inhibitor aldicarb, indicating altered activity at neuromuscular junctions. We identify a class of elements that bind EMR-1 but do not associate with LMN-1, and these are enriched for muscle and neuronal genes. Our data support a redundant function of EMR-1 and LEM-2 in chromatin anchoring to the nuclear envelope and gene repression. We demonstrate a specific role of EMR-1 in neuromuscular junction activity that may contribute to Emery-Dreifuss muscular dystrophy in humans.
    Genome biology 02/2014; 15(2):R21. DOI:10.1186/gb-2014-15-2-r21 · 10.81 Impact Factor
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