scholarly journals A role for the eIF4E-binding protein 4E-T in P-body formation and mRNA decay

2005 ◽  
Vol 170 (6) ◽  
pp. 913-924 ◽  
Author(s):  
Maria A. Ferraiuolo ◽  
Sanjukta Basak ◽  
Josee Dostie ◽  
Elizabeth L. Murray ◽  
Daniel R. Schoenberg ◽  
...  
Keyword(s):  
Mrna Decay ◽  
Binding Protein ◽  
Initiation Factor ◽  
Binding Motif ◽  
Processing Bodies ◽  
Mrna Decapping ◽  
P Bodies ◽  
Eukaryotic Initiation Factor 4E ◽  
Messenger Ribonucleoprotein ◽  
Bona Fide

4E-transporter (4E-T) is one of several proteins that bind the mRNA 5′cap-binding protein, eukaryotic initiation factor 4E (eIF4E), through a conserved binding motif. We previously showed that 4E-T is a nucleocytoplasmic shuttling protein, which mediates the import of eIF4E into the nucleus. At steady state, 4E-T is predominantly cytoplasmic and is concentrated in bodies that conspicuously resemble the recently described processing bodies (P-bodies), which are believed to be sites of mRNA decay. In this paper, we demonstrate that 4E-T colocalizes with mRNA decapping factors in bona fide P-bodies. Moreover, 4E-T controls mRNA half-life, because its depletion from cells using short interfering RNA increases mRNA stability. The 4E-T binding partner, eIF4E, also is localized in P-bodies. 4E-T interaction with eIF4E represses translation, which is believed to be a prerequisite for targeting of mRNAs to P-bodies. Collectively, these data suggest that 4E-T interaction with eIF4E is a priming event in inducing messenger ribonucleoprotein rearrangement and transition from translation to decay.

scholarly journals The DEAD-Box RNA Helicase Ded1p Affects and Accumulates inSaccharomyces cerevisiaeP-Bodies

2008 ◽  
Vol 19 (3) ◽  
pp. 984-993 ◽  
Author(s):  
Carla Beckham ◽  
Angela Hilliker ◽  
Anne-Marie Cziko ◽  
Amine Noueiry ◽  
Mani Ramaswami ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Processing Bodies ◽  
Body Formation ◽  
P Bodies ◽  
Dead Box ◽  
Inhibition Of Growth ◽  
Messenger Ribonucleoprotein ◽  
Positive Effect

Recent results suggest that cytoplasmic mRNAs can form translationally repressed messenger ribonucleoprotein particles (mRNPs) capable of decapping and degradation, or accumulation into cytoplasmic processing bodies (P-bodies), which can function as sites of mRNA storage. The proteins that function in transitions between the translationally repressed mRNPs that accumulate in P-bodies and mRNPs engaged in translation are largely unknown. Herein, we demonstrate that the yeast translation initiation factor Ded1p can localize to P-bodies. Moreover, depletion of Ded1p leads to defects in P-body formation. Overexpression of Ded1p results in increased size and number of P-bodies and inhibition of growth in a manner partially suppressed by loss of Pat1p, Dhh1p, or Lsm1p. Mutations that inactivate the ATPase activity of Ded1p increase the overexpression growth inhibition of Ded1p and prevent Ded1p from localizing in P-bodies. Combined with earlier work showing Ded1p can have a positive effect on translation, these results suggest that Ded1p is a bifunctional protein that can affect both translation initiation and P-body formation.

scholarly journals IP6K1 upregulates the formation of processing bodies by promoting proteome remodeling on the mRNA cap

2020 ◽  
Author(s):  
Akruti Shah ◽  
Rashna Bhandari
Keyword(s):  
Protein Interactions ◽  
Inositol Phosphate ◽  
Binding Protein ◽  
Mrna Translation ◽  
Rna Helicase ◽  
Scaffolding Protein ◽  
Processing Bodies ◽  
Activator Proteins ◽  
Mrna Decapping ◽  
P Bodies

AbstractInositol hexakisphosphate kinases (IP6Ks) are ubiquitously expressed small molecule kinases that catalyze the conversion of the inositol phosphate IP6 to 5-IP7. IP6Ks have been reported to influence cellular functions by protein-protein interactions independent of their enzymatic activity. Here, we show that IP6K1 regulates the formation of processing bodies (P-bodies), which are cytoplasmic ribonucleoprotein granules that serve as sites for storage of translationally repressed mRNA. Cells with reduced levels of IP6K1 display a dramatic reduction in the number of P-bodies, which can be restored by the expression of active or catalytically inactive IP6K1. IP6K1 does not localize to P-bodies, but instead facilitates the formation of P-bodies by promoting translation suppression. We demonstrate that IP6K1 is present on ribosomes, where it interacts with proteins that constitute the mRNA decapping complex – the scaffold protein EDC4, activator proteins DCP1A/B, and the decapping enzyme DCP2. IP6K1 also interacts with components of the eIF4F translation initiation complex – the scaffolding protein eIF4G1, the RNA helicase eIF4A2, and the cap binding protein eIF4E. The RNA helicase DDX6 and the eIF4E binding protein 4E-T are known to promote translation suppression to facilitate P-body formation. We show that IP6K1 binds to DDX6 and promotes the interaction of DDX6 and 4E-T with the cap binding protein eIF4E, and also enhances the binding between DDX6 and EDC4, thus acting to suppress mRNA translation and promote mRNA decapping. Our findings unveil IP6K1 as a novel facilitator of proteome remodelling on the mRNA cap, tipping the balance in favour of translation repression over initiation, and thus leading to the formation of P-bodies.

scholarly journals Human TOB, an Antiproliferative Transcription Factor, Is a Poly(A)-Binding Protein-Dependent Positive Regulator of Cytoplasmic mRNA Deadenylation

2007 ◽  
Vol 27 (22) ◽  
pp. 7791-7801 ◽  
Author(s):  
Nader Ezzeddine ◽  
Tsung-Cheng Chang ◽  
Wenmiao Zhu ◽  
Akio Yamashita ◽  
Chyi-Ying A. Chen ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Mammalian Cells ◽  
Mrna Decay ◽  
Binding Protein ◽  
Processing Bodies ◽  
Protein Motifs ◽  
P Bodies ◽  
3T3 Fibroblasts ◽  
A Site

ABSTRACT In mammalian cells, mRNA decay begins with deadenylation, which involves two consecutive phases mediated by the PAN2-PAN3 and the CCR4-CAF1 complexes, respectively. The regulation of the critical deadenylation step and its relationship with RNA-processing bodies (P-bodies), which are thought to be a site where poly(A)-shortened mRNAs get degraded, are poorly understood. Using the Tet-Off transcriptional pulsing approach to investigate mRNA decay in mouse NIH 3T3 fibroblasts, we found that TOB, an antiproliferative transcription factor, enhances mRNA deadenylation in vivo. Results from glutathione S-transferase pull-down and coimmunoprecipitation experiments indicate that TOB can simultaneously interact with the poly(A) nuclease complex CCR4-CAF1 and the cytoplasmic poly(A)-binding protein, PABPC1. Combining these findings with those from mutagenesis studies, we further identified the protein motifs on TOB and PABPC1 that are necessary for their interaction and found that interaction with PABPC1 is necessary for TOB's deadenylation-enhancing effect. Moreover, our immunofluorescence microscopy results revealed that TOB colocalizes with P-bodies, suggesting a role of TOB in linking deadenylation to the P-bodies. Our findings reveal a new mechanism by which the fate of mammalian mRNA is modulated at the deadenylation step by a protein that recruits poly(A) nuclease(s) to the 3′ poly(A) tail-PABP complex.

scholarly journals Cap-binding protein (eukaryotic initiation factor 4E) and 4E-inactivating protein BP-1 independently regulate cap-dependent translation.

1996 ◽  
Vol 16 (10) ◽  
pp. 5450-5457 ◽  
Author(s):  
D Feigenblum ◽  
R J Schneider
Keyword(s):  
Heat Shock ◽  
Translation Initiation ◽  
Binding Protein ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Metaphase Arrest ◽  
Animal Cells ◽  
Eukaryotic Initiation Factor 4E ◽  
Dependent Protein

Cap-dependent protein synthesis in animal cells is inhibited by heat shock, serum deprivation, metaphase arrest, and infection with certain viruses such as adenovirus (Ad). At a mechanistic level, translation of capped mRNAs is inhibited by dephosphorylation of eukaryotic initiation factor 4E (eIF-4E) (cap-binding protein) and its physical sequestration with the translation repressor protein BP-1 (PHAS-I). Dephosphorylation of BP-I blocks cap-dependent translation by promoting sequestration of eIF-4E. Here we show that heat shock inhibits translation of capped mRNAs by simultaneously inducing dephosphorylation of eIF-4E and BP-1, suggesting that cells might coordinately regulate translation of capped mRNAs by impairing both the activity and the availability of eIF-4E. Like heat shock, late Ad infection is shown to induce dephosphorylation of eIF-4E. However, in contrast to heat shock, Ad also induces phosphorylation of BP-1 and release of eIF-4E. BP-1 and eIF-4E can therefore act on cap-dependent translation in either a mutually antagonistic or cooperative manner. Three sets of experiments further underscore this point: (i) rapamycin is shown to block phosphorylation of BP-1 without inhibiting dephosphorylation of eIF-4E induced by heat shock or Ad infection, (ii) eIF-4E is efficiently dephosphorylated during heat shock or Ad infection regardless of whether it is in a complex with BP-1, and (iii) BP-1 is associated with eIF-4E in vivo regardless of the state of eIF-4E phosphorylation. These and other studies establish that inhibition of cap-dependent translation does not obligatorily involve sequestration of eIF-4E by BP-1. Rather, translation is independently regulated by the phosphorylation states of eIF-4E and the 4E-binding protein, BP-1. In addition, these results demonstrate that BP-1 and eIF-4E can act either in concert or in opposition to independently regulate cap-dependent translation. We suggest that independent regulation of eIF-4E and BP-1 might finely regulate the efficiency of translation initiation or possibly control cap-dependent translation for fundamentally different purposes.

On track with P-bodies

2010 ◽  
Vol 38 (1) ◽  
pp. 242-251 ◽  
Author(s):  
Meeta Kulkarni ◽  
Sevim Ozgur ◽  
Georg Stoecklin
Keyword(s):  
Light Microscopy ◽  
Mrna Decay ◽  
Molecular Level ◽  
Somatic Cells ◽  
Present Review ◽  
Dual Function ◽  
Processing Bodies ◽  
P Bodies ◽  
Specific Mrnas ◽  
Transient Interactions

P-bodies (processing bodies) are cytoplasmic foci visible by light microscopy in somatic cells of vertebrate and invertebrate origin as well as in yeast, plants and trypanosomes. At the molecular level, P-bodies are dynamic aggregates of specific mRNAs and proteins that serve a dual function: first, they harbour mRNAs that are translationally silenced, and such mRNA can exit again from P-bodies to re-engage in translation. Secondly, P-bodies recruit mRNAs that are targeted for deadenylation and degradation by the decapping/Xrn1 pathway. Whereas certain proteins are core constituents of P-bodies, others involved in recognizing short-lived mRNAs can only be trapped in P-bodies when mRNA decay is attenuated. This reflects the very transient interactions by which many proteins associate with P-bodies. In the present review, we summarize recent findings on the function, assembly and motility of P-bodies. An updated list of proteins and RNAs that localize to P-bodies will help in keeping track of this fast-growing field.

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