Article

Targeting of Aberrant mRNAs to Cytoplasmic Processing Bodies

Department of Molecular and Cellular Biology, University of Arizona, Tucson, 85721, USA.
Cell (Impact Factor: 32.24). 07/2006; 125(6):1095-109. DOI: 10.1016/j.cell.2006.04.037
Source: PubMed

ABSTRACT

In eukaryotes, a specialized pathway of mRNA degradation termed nonsense-mediated decay (NMD) functions in mRNA quality control by recognizing and degrading mRNAs with aberrant termination codons. We demonstrate that NMD in yeast targets premature termination codon (PTC)-containing mRNA to P-bodies. Upf1p is sufficient for targeting mRNAs to P-bodies, whereas Upf2p and Upf3p act, at least in part, downstream of P-body targeting to trigger decapping. The ATPase activity of Upf1p is required for NMD after the targeting of mRNAs to P-bodies. Moreover, Upf1p can target normal mRNAs to P-bodies but not promote their degradation. These observations lead us to propose a new model for NMD wherein two successive steps are used to distinguish normal and aberrant mRNAs.

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    • "Finally, the Saccharomyces cerevisiae ortholog Dhh1 is able to repress translation (Carroll et al., 2011; Coller and Parker, 2005), but its best studied function is in the enhancement of mRNA decapping and decay (Coller et al., 2001; Fischer and Weis, 2002). In tissue culture cells, all DDX6 orthologs studied to date localize in RNP aggregates known as processing (P)bodies , which also contain RNA decay factors (Anderson and Kedersha, 2006; Eulalio et al., 2007; Sheth and Parker, 2006). DDX6 is a very abundant protein that belongs to the DEAD-box family of RNA-dependent ATPases (Ozgur et al., 2015; Presnyak and Coller, 2013; Russell et al., 2013). "
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    ABSTRACT: The DEAD-box protein DDX6 is a central component of translational repression mechanisms in maternal mRNA storage in oocytes and microRNA-mediated silencing in somatic cells. DDX6 interacts with the CCR4-NOT complex and functions in concert with several post-transcriptional regulators, including Edc3, Pat1, and 4E-T. We show that the conserved CUP-homology domain (CHD) of human 4E-T interacts directly with DDX6 in both the presence and absence of the central MIF4G domain of CNOT1. The 2.1-Å resolution structure of the corresponding ternary complex reveals how 4E-T CHD wraps around the RecA2 domain of DDX6 and contacts CNOT1. Although 4E-T CHD lacks recognizable sequence similarity with Edc3 or Pat1, it shares the same DDX6-binding surface. In contrast to 4E-T, however, the Edc3 and Pat1 FDF motifs dissociate from DDX6 upon CNOT1 MIF4G binding in vitro. The results underscore the presence of a complex network of simultaneous and/or mutually exclusive interactions in DDX6-mediated repression.
    Full-text · Article · Oct 2015 · Cell Reports
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    • "Many proteins that are involved in mRNA decay, such as CCR4-NOT deadenylase components, DCP2, PATL1, EDC3, DDX6, and LSM14, are enriched in dynamic cytoplasmic foci called processing bodies (P-bodies) (Kedersha and Anderson, 2009; Sheth and Parker, 2006). A key protein that promotes P-body formation is the eIF4E-transporter protein, 4E-T (Ferraiuolo et al., 2005). "
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    ABSTRACT: Eukaryotic mRNA degradation often initiates with the recruitment of the CCR4-NOT deadenylase complex and decay factors to the mRNA 3' terminus. How the 3'-proximal decay machinery interacts with the 5'-terminal cap structure in order to engender mRNA decapping and 5'-3' degradation is unclear. Human 4E-T is an eIF4E-binding protein that has been reported to promote mRNA decay, albeit via an unknown mechanism. Here, we show that 4E-T is a component of the mRNA decay machinery and interacts with factors including DDX6, LSM14, and the LSM1-7-PAT1 complex. We also provide evidence that 4E-T associates with, and enhances the decay of, mRNAs targeted by the CCR4-NOT deadenylase complex, including microRNA targets. Importantly, we demonstrate that 4E-T must interact with eIF4E to engender mRNA decay. Taken together, our data support a model where 4E-T promotes mRNA turnover by physically linking the 3'-terminal mRNA decay machinery to the 5' cap via its interaction with eIF4E. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
    Full-text · Article · May 2015 · Cell Reports
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    • "The up-frameshift proteins UPF1, UPF2, and UPF3 are essential factors of NMD. In yeast, UPF1-3 are involved in recognition and targeting PTC-containing mRNA to PB (Sheth and Parker, 2006; Nyikó et al., 2009). UPF1-3 are cytoplasmic, but they co-localize to DCP2 in the dcp1Δ strain, theoretically by accumulation of non-degraded aberrant mRNAs or other substrates of NMD. "
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    ABSTRACT: mRNA accumulation is tightly regulated by diverse molecular pathways. The identification and characterization of enzymes and regulatory proteins involved in controlling the fate of mRNA offers the possibility to broaden our understanding of posttranscriptional gene regulation. Processing bodies (P bodies, PB) are cytoplasmic protein complexes involved in degradation and translational arrest of mRNA. Composition and dynamics of these subcellular structures have been studied in animal systems, yeasts and in the model plant Arabidopsis. Their assembly implies the aggregation of specific factors related to decapping, deadenylation, and exoribonucleases that operate synchronously to regulate certain mRNA targets during development and adaptation to stress. Although the general function of PB along with the flow of genetic information is understood, several questions still remain open. This review summarizes data on the composition, potential molecular roles, and biological significance of PB and potentially related proteins in Arabidopsis.
    Full-text · Article · May 2014 · Frontiers in Plant Science
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