更新于：2024-05-01

NEMF

nuclear export mediator factor

更新于：2024-05-01

基本信息

别名

Antigen NY-CO-1、FLJ10051、NEMF

+ [5]

简介

Key component of the ribosome quality control complex (RQC), a ribosome-associated complex that mediates the extraction of incompletely synthesized nascent chains from stalled ribosomes as well as their ubiquitin-mediated proteasomal degradation (PubMed:25578875, PubMed:32726578, PubMed:33406423, PubMed:33909987). Thereby, frees 60S subunit ribosomes from the stalled translation complex and prevents the accumulation of nascent polypeptide chains that are potentially toxic for the cell (PubMed:25578875, PubMed:33406423, PubMed:33909987). Within the RQC complex, NEMF specifically binds stalled 60S ribosomal subunits by recognizing an exposed, nascent chain-conjugated tRNA moiety and promotes the recruitment of LTN1 to stalled 60S subunits (PubMed:25578875). Following binding to stalled 60S ribosomal subunits, NEMF mediates CAT tailing by recruiting alanine-charged tRNA to the A-site and directing the elongation of stalled nascent chains independently of mRNA or 40S subunits, leading to non-templated C-terminal alanine extensions (CAT tails) (PubMed:33406423, PubMed:33909987). Mainly recruits alanine-charged tRNAs, but can also other amino acid-charged tRNAs (PubMed:33406423, PubMed:33909987). CAT tailing is required to promote ubiquitination of stalled nascent chains by different E3 ubiquitin-protein ligases (PubMed:33909987). In the canonical RQC pathway (RQC-L), CAT tailing facilitates LTN1-dependent ubiquitination by exposing lysine residues that would otherwise remain buried in the ribosomal exit tunnel (By similarity). In the alternative RQC pathway (RQC-C) CAT tailing creates an C-degron mainly composed of alanine that is recognized by the CRL2(KLHDC10) and RCHY1/PIRH2 E3 ligases, leading to ubiquitination and degradation of stalled nascent chains (PubMed:33909987). NEMF may also indirectly play a role in nuclear export (PubMed:16103875).

关联

100 项与 NEMF 相关的临床结果

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100 项与 NEMF 相关的转化医学

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0 项与 NEMF 相关的专利（医药）

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项与 NEMF 相关的文献（医药）

2024-01-16·Scientific reports

Transcriptional profile of ribosome-associated quality control components and their associated phenotypes in mammalian cells.

Article

作者: Otávio Augusto Leitão Dos Santos ; Rodolfo L Carneiro ; Rodrigo D Requião ; Marcelo Ribeiro-Alves ; Tatiana Domitrovic ; Fernando L Palhano

During protein synthesis, organisms detect translation defects that induce ribosome stalling and result in protein aggregation. The Ribosome-associated Quality Control (RQC) complex, comprising TCF25, LTN1, and NEMF, is responsible for identifying incomplete protein products from unproductive translation events, targeting them for degradation. Although RQC disruption causes adverse effects on vertebrate neurons, data regarding mRNA/protein expression and regulation across tissues are lacking. Employing high-throughput methods, we analyzed public datasets to explore RQC gene expression and phenotypes. Our findings revealed widespread expression of RQC components in human tissues; however, silencing of RQC yielded only mild negative effects on cell growth. Notably, TCF25 exhibited elevated mRNA levels that were not reflected in the protein content. We experimentally demonstrated that this disparity arose from post-translational protein degradation by the proteasome. Additionally, we observed that cellular aging marginally influenced RQC expression, leading to reduced mRNA levels in specific tissues. Our results suggest the necessity of RQC expression in all mammalian tissues. Nevertheless, when RQC falters, alternative mechanisms seem to compensate, ensuring cell survival under nonstress conditions.

2023-12-18·Journal of medicinal chemistry

Discovery of a Hidden Pocket beneath the NES Groove by Novel Noncovalent CRM1 Inhibitors.

Article

作者: Cong Li ; Qian Zhang ; Wenxin Huang ; Luyi Huang ; Qing Long ; Yuqin Lei ; Da Jia ; Shengyong Yang ; Yang Yang ; Xia Zhang ; Qingxiang Sun

Protein localization is frequently manipulated to favor tumor initiation and progression. In cancer cells, the nuclear export factor CRM1 is often overexpressed and aberrantly localizes many tumor suppressors via protein-protein interactions. Although targeting protein-protein interactions is usually challenging, covalent inhibitors, including the FDA-approved drug KPT-330 (selinexor), were successfully developed. The development of noncovalent CRM1 inhibitors remains scarce. Here, by shifting the side chain of two methionine residues and virtually screening against a large compound library, we successfully identified a series of noncovalent CRM1 inhibitors with a stable scaffold. Crystal structures of inhibitor-protein complexes revealed that one of the compounds, B28, utilized a deeply hidden protein interior cavity for binding. SAR analysis guided the development of several B28 derivatives with enhanced inhibition on nuclear export and growth of multiple cancer cell lines. This work may benefit the development of new CRM1-targeted therapies.

2023-06-07·bioRxiv : the preprint server for biology

Ribosomal quality control factors inhibit repeat-associated non-AUG translation from GC-rich repeats.

作者: Yi-Ju Tseng ; Indranil Malik ; Xiexiong Deng ; Amy Krans ; Karen Jansen-West ; Elizabeth M H Tank ; Nicolas B Gomez ; Roger Sher ; Leonard Petrucelli ; Sami J Barmada ; Peter K Todd

A GGGGCC (G4C2) hexanucleotide repeat expansion in C9ORF72 causes amyotrophic lateral sclerosis and frontotemporal dementia (C9ALS/FTD), while a CGG trinucleotide repeat expansion in FMR1 leads to the neurodegenerative disorder Fragile X-associated tremor/ataxia syndrome (FXTAS). These GC-rich repeats form RNA secondary structures that support repeat-associated non-AUG (RAN) translation of toxic proteins that contribute to disease pathogenesis. Here we assessed whether these same repeats might trigger stalling and interfere with translational elongation. We find that depletion of ribosome-associated quality control (RQC) factors NEMF, LTN1, and ANKZF1 markedly boost RAN translation product accumulation from both G4C2 and CGG repeats while overexpression of these factors reduces RAN production in both reporter cell lines and C9ALS/FTD patient iPSC-derived neurons. We also detected partially made products from both G4C2 and CGG repeats whose abundance increased with RQC factor depletion. Repeat RNA sequence, rather than amino acid content, is central to the impact of RQC factor depletion on RAN translation - suggesting a role for RNA secondary structure in these processes. Together, these findings suggest that ribosomal stalling and RQC pathway activation during RAN translation elongation inhibits the generation of toxic RAN products. We propose augmenting RQC activity as a therapeutic strategy in GC-rich repeat expansion disorders.

项与 NEMF 相关的新闻（医药）

2023-12-24

·生物制品圈

高成江团队揭示LTN1在负调控kongRLR介导的抗病毒先天免疫中的作用

病毒性传染病严重危害人类生存和健康，宿主免疫监测系统通过模式识别受体（PRRs）检测病毒核酸。RIG-I（RNA传感器RIG-I）样受体（RLRs）是负责快速识别病毒RNA的细胞质RNA解旋酶。在细胞质中识别病毒衍生的RNA后，RIG-I和MDA5与关键的衔接分子MAVS（线粒体抗病毒信号蛋白）相互作用，传递病毒信号。MAVS随后在线粒体上迅速形成朊病毒样聚集体，以触发下游TBK1和IRF3的激活，从而进一步诱导I型干扰素（IFN）和干扰素刺激基因（ISG）的产生。RIG-I和MDA5的适度表达和激活对于诱导抗病毒先天免疫反应和促进IFN-β分泌至关重要。然而，不受抑制的RIG-I和MDA5的表达可能通过诱导RLR诱导的信号过度激活而导致自身炎症和自身免疫性疾病。因此，RLR信号传导的严格调控对于确保在没有有害免疫病理学的情况下成功消除病毒至关重要。运输所需的内体分选复合物（ESCRT）系统能够捕获泛素化的蛋白质，并将其分选到晚期内体的管腔内小泡中。这些小泡成熟为多泡体/MVBs，最终与溶酶体融合促使蛋白质降解。然而，ESCRT系统在RLRs降解中的作用目前尚不清楚。近日，山东大学基础医学院高成江教授团队在Autophagy在线发表题为 LTN1 promotes RLR degradation to inhibit immune response to RNA virus through the ESCRT pathway 的研究成果，揭示了RIG-I和MDA5降解的新机制，并确定了LTN1在负调控RLR介导的抗病毒先天免疫中的作用，这可能为干预病毒感染提供新的靶点。病毒感染机体的大量复制会触发核糖体相关蛋白质量控制（ribosome-associated quality control，RQC）系统活化，导致宿主蛋白质合成稳态失衡，但RQC系统在抗病毒免疫反应中的功能和调控机制并不清楚，因此作者首先验证了RQC系统核心组分LTN1的抗病毒功能。作者构建了LTN1条件敲除小鼠，通过体外培养腹腔巨噬细胞、骨髓来源的巨噬细胞，用5’PPP-RNA、SeV、EMCV等分别刺激，发现LTN1敲除的巨噬细胞表达I型干扰素的能力增强；LTN1缺失后，VSV病毒的复制受到抑制。通过免疫印迹实验发现RLR信号通路中IRF3和TBK1的磷酸化在敲除LTN1的细胞中明显升高，这表明敲除LTN1促进了RLRs信号通路的激活进而促进了I型干扰素的产生。作者进一步研究了LTN1在体内抗病毒反应中的生理意义。相比于野生型小鼠，作者发现在LTN1敲除小鼠血清中VSV病毒诱导的IFNB的分泌明显升高，小鼠的脾脏、肝脏和肺中，Ifnb1的表达上调，VSV病毒的复制和滴度的明显降低，VSV感染后观察到严重的肺损伤相比于野生型小鼠明显减轻，死亡率下降。这些发现表明LTN1缺陷小鼠比野生型小鼠更能抵抗RNA病毒感染。为了揭示LTN1抑制RLR介导的免疫的分子机制，作者通过qRT-PCR，免疫共沉淀，免疫荧光等实验技术明确LTN1的靶点为RIG-I及MDA5，并促进两者降解。RQC系统关键组分NEMF、TCF25可与LTN1形成复合物帮助有缺陷或异常的多肽降解。因此作者分别构建了NEMF、TCF25 293T敲除细胞系，研究发现敲除NEMF或TCF25，LTN1仍就促进的RIG-I和MDA5蛋白降解。这提示LTN1可能独立于RQC系统发挥新功能。作者进一步研究发现，LTN1与RIG-I及MDA5在内体上存在共定位，ESCRT-0包括HGS和STAM，它们对于将泛素化的物质分选到内体中至关重要。作者在细胞中敲低或者敲除HGS和STAM组分，LTN1不再促进的RIG-I和MDA5蛋白降解。这些数据表明LTN1通过ESCRT系统介导RIG-I和MDA5的降解。LTN1是一种参与核糖体异常新生链泛素化修饰的E3泛素连接酶，同时ESCRT系统也主要降解泛素化的蛋白。因此，作者接下来探究了LTN1介导的RIG-I和MDA5的降解是否通过蛋白泛素化发生。通过免疫共沉淀实验，作者发现LTN1 明显增加了RIG-I和MDA5的K63链接的泛素化水平，但是LTN1缺失RING结构域或酶活位点突变后仍然可以增加RIG-I和MDA5的泛素化水平，这些数据表明，LTN1独立于其E3酶活性促进RIG-I和MDA5的多泛素化。因此作者假设LTN1可能招募其他E3连接酶进行K63连接的多泛素化。通过对LTN1相互作用蛋白的质谱分析，作者发现E3泛素连接酶TRIM27是LTN1潜在的候选结合蛋白。进一步通过重组蛋白体外结合实验显示TRIM27不能直接与RIG-I和MDA5相互作用，LTN1促进了TRIM27与RIG-I和MDA5的相互作用。体外泛素化实验表明LTN1招募E3泛素连接酶TRIM27促进了RIG-I和MDA5的泛素化。在这项研究中，作者发现LTN1可以增加RIG-I和MDA5的K63连接的多泛素化。这种K63连接的多泛素化通过ESCRT依赖性途径促进RIG-I和MDA5蛋白的分选和降解。进一步的通过质谱发现LTN1通过招募E3泛素连接酶TRIM27介导了RIG-I和MDA5的K63连接的多泛素化。LTN1敲除能够促进小鼠对RNA病毒感染的先天抗病毒免疫反应。因此，该工作揭示了RIG-I和MDA5降解的新机制，并确定了LTN1在负调控RLR介导的抗病毒先天免疫中的作用，这可能为病毒感染的干预提供新的靶点。山东大学基础医学院博士研究生秦菲、蔡宝珊为本文共同第一作者，山东大学高成江教授、刘冰玉教授为共同通讯作者。原文链接：https://www-tandfonline-com.libproxy1.nus.edu.sg/doi/full/10.1080/15548627.2023.2291939识别微信二维码，添加生物制品圈小编，符合条件者即可加入生物制品微信群！请注明：姓名+研究方向！版权声明本公众号所有转载文章系出于传递更多信息之目的，且明确注明来源和作者，不希望被转载的媒体或个人可与我们联系(cbplib@163.com)，我们将立即进行删除处理。所有文章仅代表作者观点，不代表本站立场。