scholarly journals PGL proteins self associate and bind RNPs to mediate germ granule assembly in C. elegans

2011 ◽  
Vol 192 (6) ◽  
pp. 929-937 ◽  
Author(s):  
Momoyo Hanazawa ◽  
Masafumi Yonetani ◽  
Asako Sugimoto
Keyword(s):  
Mammalian Cells ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Function Analysis ◽  
General Mechanism ◽  
Granule Formation ◽  
C Elegans ◽  
Germ Granules ◽  
Self Association

Germ granules are germ lineage–specific ribonucleoprotein (RNP) complexes, but how they are assembled and specifically segregated to germ lineage cells remains unclear. Here, we show that the PGL proteins PGL-1 and PGL-3 serve as the scaffold for germ granule formation in Caenorhabditis elegans. Using cultured mammalian cells, we found that PGL proteins have the ability to self-associate and recruit RNPs. Depletion of PGL proteins from early C. elegans embryos caused dispersal of other germ granule components in the cytoplasm, suggesting that PGL proteins are essential for the architecture of germ granules. Using a structure–function analysis in vivo, we found that two functional domains of PGL proteins contribute to germ granule assembly: an RGG box for recruiting RNA and RNA-binding proteins and a self-association domain for formation of globular granules. We propose that self-association of scaffold proteins that can bind to RNPs is a general mechanism by which large RNP granules are formed.

scholarly journals Structure-Function Analysis of Qk1: a Lethal Point Mutation in Mouse quaking Prevents Homodimerization

1998 ◽  
Vol 18 (8) ◽  
pp. 4863-4871 ◽  
Author(s):  
Taiping Chen ◽  
Stéphane Richard
Keyword(s):  
Glutamic Acid ◽  
Point Mutation ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Function Analysis ◽  
Binding Activity ◽  
Kh Domain ◽  
Self Association ◽  
Nih 3T3

ABSTRACT Qk1 is a member of the KH domain family of proteins that includes Sam68, GRP33, GLD-1, SF1, and Who/How. These family members are RNA binding proteins that contain an extended KH domain embedded in a larger domain called the GSG (for GRP33–Sam68–GLD-1) domain. An ethylnitrosourea-induced point mutation in the Qk1 GSG domain alters glutamic acid 48 to a glycine and is known to be embryonically lethal in mice. The function of Qk1 and the GSG domain as well as the reason for the lethality are unknown. Here we demonstrate that the Qk1 GSG domain mediates RNA binding and Qk1 self-association. By using in situ chemical cross-linking studies, we showed that the Qk1 proteins exist as homodimers in vivo. The Qk1 self-association region was mapped to amino acids 18 to 57, a region predicted to form coiled coils. Alteration of glutamic acid 48 to glycine (E➤G) in the Qk1 GSG domain (producing protein Qk1:E➤G) abolishes self-association but has no effect on the RNA binding activity. The expression of Qk1 or Qk1:E➤G in NIH 3T3 cells induces cell death by apoptosis. Approximately 90% of the remaining transfected cells are apoptotic 48 h after transfection. Qk1:E➤G was consistently more potent at inducing apoptosis than was wild-type Qk1. These results suggest that the mousequaking lethality (E➤G) occurs due to the absence of Qk1 self-association mediated by the GSG domain.

scholarly journals Identification of proteins and miRNAs that specifically bind an mRNA in vivo

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Kathrin Theil ◽  
Koshi Imami ◽  
Nikolaus Rajewsky
Keyword(s):  
Rna Binding ◽  
De Novo ◽  
Rna Binding Proteins ◽  
Noncoding Rnas ◽  
Shotgun Proteomics ◽  
Small Rna Sequencing ◽  
C Elegans ◽  
Specific Transcript ◽  
Proteomics Approach

Abstract Understanding regulation of an mRNA requires knowledge of its regulators. However, methods for reliable de-novo identification of proteins binding to a particular RNA are scarce and were thus far only successfully applied to abundant noncoding RNAs in cell culture. Here, we present vIPR, an RNA-protein crosslink, RNA pulldown, and shotgun proteomics approach to identify proteins bound to selected mRNAs in C. elegans. Applying vIPR to the germline-specific transcript gld-1 led to enrichment of known and novel interactors. By comparing enrichment upon gld-1 and lin-41 pulldown, we demonstrate that vIPR recovers both common and specific RNA-binding proteins, and we validate DAZ-1 as a specific gld-1 regulator. Finally, combining vIPR with small RNA sequencing, we recover known and biologically important transcript-specific miRNA interactions, and we identify miR-84 as a specific interactor of the gld-1 transcript. We envision that vIPR will provide a platform for investigating RNA in vivo regulation in diverse biological systems.

scholarly journals RNA dependent suppression of C9orf72 ALS/FTD associated neurodegeneration by Matrin-3

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Nandini Ramesh ◽  
Elizabeth L. Daley ◽  
Amanda M. Gleixner ◽  
Jacob R. Mann ◽  
Sukhleen Kour ◽  
...  
Keyword(s):  
Motor Neurons ◽  
Mammalian Cells ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Ectopic Expression ◽  
Dependent Manner ◽  
Matrin 3 ◽  
Rna Foci ◽  
Ran Translation

Abstract The most common genetic cause of amyotrophic lateral sclerosis (ALS) is a GGGGCC (G4C2) hexanucleotide repeat expansions in first intron of the C9orf72 gene. The accumulation of repetitive RNA sequences can mediate toxicity potentially through the formation of intranuclear RNA foci that sequester key RNA-binding proteins (RBPs), and non-ATG mediated translation into toxic dipeptide protein repeats. However, the contribution of RBP sequestration to the mechanisms underlying RNA-mediated toxicity remain unknown. Here we show that the ALS-associated RNA-binding protein, Matrin-3 (MATR3), colocalizes with G4C2 RNA foci in patient tissues as well as iPSC-derived motor neurons harboring the C9orf72 mutation. Hyperexpansion of C9 repeats perturbed subcellular distribution and levels of endogenous MATR3 in C9-ALS patient-derived motor neurons. Interestingly, we observed that ectopic expression of human MATR3 strongly mitigates G4C2-mediated neurodegeneration in vivo. MATR3-mediated suppression of C9 toxicity was dependent on the RNA-binding domain of MATR3. Importantly, we found that expression of MATR3 reduced the levels of RAN-translation products in mammalian cells in an RNA-dependent manner. Finally, we have shown that knocking down endogenous MATR3 in C9-ALS patient-derived iPSC neurons decreased the presence of G4C2 RNA foci in the nucleus. Overall, these studies suggest that MATR3 genetically modifies the neuropathological and the pathobiology of C9orf72 ALS through modulating the RNA foci and RAN translation.

scholarly journals Engineering a conserved RNA regulatory protein repurposes its biological function in vivo

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Vandita D Bhat ◽  
Kathleen L McCann ◽  
Yeming Wang ◽  
Dallas R Fonseca ◽  
Tarjani Shukla ◽  
...  
Keyword(s):  
Genome Engineering ◽  
Rna Binding ◽  
Biological Function ◽  
Rna Binding Proteins ◽  
Critical Role ◽  
Regulatory Protein ◽  
Motif Length ◽  
C Elegans ◽  
Preferential Binding

PUF (PUmilio/FBF) RNA-binding proteins recognize distinct elements. In C. elegans, PUF-8 binds to an 8-nt motif and restricts proliferation in the germline. Conversely, FBF-2 recognizes a 9-nt element and promotes mitosis. To understand how motif divergence relates to biological function, we first determined a crystal structure of PUF-8. Comparison of this structure to that of FBF-2 revealed a major difference in a central repeat. We devised a modified yeast 3-hybrid screen to identify mutations that confer recognition of an 8-nt element to FBF-2. We identified several such mutants and validated structurally and biochemically their binding to 8-nt RNA elements. Using genome engineering, we generated a mutant animal with a substitution in FBF-2 that confers preferential binding to the PUF-8 element. The mutant largely rescued overproliferation in animals that spontaneously generate tumors in the absence of puf-8. This work highlights the critical role of motif length in the specification of biological function.

scholarly journals Self-association of the single-KH-domain family members Sam68, GRP33, GLD-1, and Qk1: role of the KH domain.

1997 ◽  
Vol 17 (10) ◽  
pp. 5707-5718 ◽  
Author(s):  
T Chen ◽  
B B Damaj ◽  
C Herrera ◽  
P Lasko ◽  
S Richard
Keyword(s):  
Mammalian Cells ◽  
Rna Binding ◽  
Family Members ◽  
Artemia Salina ◽  
Domain Family ◽  
Protein Motifs ◽  
Kh Domain ◽  
Self Association

Sam68 is a member of a growing family of proteins that contain a single KH domain embedded in a larger conserved domain of approximately 170 amino acids. Loops 1 and 4 of this KH domain family are longer than the corresponding loops in other KH domains and contain conserved residues. KH domains are protein motifs that are involved in RNA binding and are often present in multiple copies. Here we demonstrate by coimmunoprecipitation studies that Sam68 self-associated and that cellular RNA was required for the association. Deletion studies demonstrated that the Sam68 KH domain loops 1 and 4 were required for self-association. The Sam68 interaction was also observed in Saccharomyces cerevisiae by the two-hybrid system. In situ chemical cross-linking studies in mammalian cells demonstrated that Sam68 oligomerized in vivo. These Sam68 complexes bound homopolymeric RNA and the SH3 domains of p59fyn and phospholipase Cgamma1 in vitro, demonstrating that Sam68 associates with RNA and signaling molecules as a multimer. The formation of the Sam68 complex was inhibited by p59fyn, suggesting that tyrosine phosphorylation regulates Sam68 oligomerization. Other Sam68 family members including Artemia salina GRP33, Caenorhabditis elegans GLD-1, and mouse Qk1 also oligomerized. In addition, Sam68, GRP33, GLD-1, and Qk1 associated with other KH domain proteins such as Bicaudal C. These observations indicate that the single KH domain found in the Sam68 family, in addition to mediating protein-RNA interactions, mediates protein-protein interactions.

scholarly journals Proteins binding to 5' untranslated region sites: a general mechanism for translational regulation of mRNAs in human and yeast cells.

1994 ◽  
Vol 14 (9) ◽  
pp. 5898-5909 ◽  
Author(s):  
R Stripecke ◽  
C C Oliveira ◽  
J E McCarthy ◽  
M W Hentze
Keyword(s):  
Binding Sites ◽  
Untranslated Region ◽  
Translational Regulation ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Yeast Cells ◽  
General Mechanism ◽  
Translational Repressor

We demonstrate that a bacteriophage protein and a spliceosomal protein can be converted into eukaryotic translational repressor proteins. mRNAs with binding sites for the bacteriophage MS2 coat protein or the spliceosomal human U1A protein were expressed in human HeLa cells and yeast. The presence of the appropriate binding protein resulted in specific, dose-dependent translational repression when the binding sites were located in the 5' untranslated region (UTR) of the reporter mRNAs. Neither mRNA export from the nucleus to the cytoplasm nor mRNA stability was demonstrably affected by the binding proteins. The data thus reveal a general mechanism for translational regulation: formation of mRNA-protein complexes in the 5' UTR controls translation initiation by steric blockage of a sensitive step in the initiation pathway. Moreover, the findings establish the basis for novel strategies to study RNA-protein interactions in vivo and to clone RNA-binding proteins.

scholarly journals YB-1 regulates stress granule formation and tumor progression by translationally activating G3BP1

2015 ◽  
Vol 208 (7) ◽  
pp. 913-929 ◽  
Author(s):  
Syam Prakash Somasekharan ◽  
Amal El-Naggar ◽  
Gabriel Leprivier ◽  
Hongwei Cheng ◽  
Shamil Hajee ◽  
...  
Keyword(s):  
Tumor Progression ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Critical Role ◽  
Granule Formation ◽  
Ribonucleoprotein Complexes ◽  
Highly Correlated ◽  
As Stress

Under cell stress, global protein synthesis is inhibited to preserve energy. One mechanism is to sequester and silence mRNAs in ribonucleoprotein complexes known as stress granules (SGs), which contain translationally silent mRNAs, preinitiation factors, and RNA-binding proteins. Y-box binding protein 1 (YB-1) localizes to SGs, but its role in SG biology is unknown. We now report that YB-1 directly binds to and translationally activates the 5′ untranslated region (UTR) of G3BP1 mRNAs, thereby controlling the availability of the G3BP1 SG nucleator for SG assembly. YB-1 inactivation in human sarcoma cells dramatically reduces G3BP1 and SG formation in vitro. YB-1 and G3BP1 expression are highly correlated in human sarcomas, and elevated G3BP1 expression correlates with poor survival. Finally, G3BP1 down-regulation in sarcoma xenografts prevents in vivo SG formation and tumor invasion, and completely blocks lung metastasis in mouse models. Together, these findings demonstrate a critical role for YB-1 in SG formation through translational activation of G3BP1, and highlight novel functions for SGs in tumor progression.

scholarly journals Germline RNA helicases couple RNA binding to P granule assembly at nuclear periphery

2019 ◽  
Author(s):  
Wenjun Chen ◽  
Yabing Hu ◽  
Charles Lang ◽  
Jordan S Brown ◽  
Xiaoyan Song ◽  
...  
Keyword(s):  
Cell Fate ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Nuclear Periphery ◽  
Liquid Droplets ◽  
Rna Helicases ◽  
Granule Formation ◽  
P Granules ◽  
Germ Granules ◽  
Germline Rna Helicases

ABSTRACTP granules are phase-separated liquid droplets that play important roles in the maintenance of the germ cell fate in C. elegans. The localization and formation of P granules are highly dynamic, but mechanisms that regulate such processes remain poorly understood. Here we show that germline RNA helicases (GLHs) control the formation and disassembly of germ granules through their binding and release of RNAs, respectively. In addition, the FGG repeats in the GLHs promote the formation of germ granules at the perinucleus. Proteomic analyses of a mutation that traps RNA-bound GLH-1 complex revealed transient interactions of GLH-1 with several Argonautes and RNA binding proteins. Finally, we found that defects in perinuclear P granule formation correlate with the fertility defects observed in various GLH mutants. Together, our results highlight the versatile roles of RNA helicases in controlling the formation of liquid droplets in space and time.

scholarly journals Active role of free RNA during the early phase of proteostasis stress

2019 ◽  
Author(s):  
Marion Alriquet ◽  
Adrían Martínez-Limón ◽  
Gerd Hanspach ◽  
Martin Hengesbach ◽  
Gian G. Tartaglia ◽  
...  
Keyword(s):  
Rna Binding ◽  
Rna Binding Proteins ◽  
Active Form ◽  
Active Role ◽  
Structural Features ◽  
Cellular Functions ◽  
Granule Formation

ABSTRACTTransient sequestration of proteins and RNA is an essential principle of cellular reaction to stress. Compared to polypeptides, less is known about the role of RNA released from polysomes during acute proteostasis stress. Using quantitative mass spectrometry, we identified a set of proteins assembled by free RNA in the heat-shocked mammalian cytosol. RNA-associated proteins displayed higher disorder and larger size, which supports the role of multivalent interactions during the initial phase of the RNA granule formation. Structural features of the free RNA interactors defined them as a subset of RNA-binding proteins. The interactome contained preferentially the active form of eIF2α. The interaction between assembled proteins in vivo required RNA. The reconstitution of the association process in vitro indicated to the multimolecular basis for the increased binding to RNA upon heat shock in the cytosol. Our results reveal how free RNA can participate in reorganization of cellular functions during proteostasis stress.

scholarly journals Distinct phases within large RNP granules of C. elegans oocytes are associated with differential stress responses of RNA binding proteins

2021 ◽  
Author(s):  
Brooklynne Watkins ◽  
Mohamed T. Elaswad ◽  
Chloe Pestrue ◽  
Katherine Sharp ◽  
Elizabeth Breton ◽  
...  
Keyword(s):  
Stress Responses ◽  
Binding Proteins ◽  
Rna Binding ◽  
Intermediate Phase ◽  
Rna Binding Proteins ◽  
Oocyte Quality ◽  
C Elegans ◽  
Disease States ◽  
Germ Granules ◽  
Rnp Granules

One emerging paradigm of cellular organization of RNA and RNA binding proteins is the formation of membraneless organelles (MLOs). Examples of MLOs include several types of RNP (ribonucleoprotein) granules that form via phase separation. Proper regulation of the phase transitions of RNA binding proteins is critical as dysregulation can lead to disease states. Germ granules are small RNP granules conserved across metazoa. In C. elegans, when oogenesis undergoes an extended meiotic arrest, germ granules assemble into much larger, more complex RNP granules whose hypothesized function is to regulate RNA metabolism and maintain oocyte quality. As a step towards gaining insight into the function of RNP granules, in this report we characterize distinct phases for four RNA binding proteins in arrested oocytes. We find that PGL-1 is dynamic and has liquid-like properties, while MEG-3 has gel-like properties, both similar to their properties in small germ granules of embryos. We also show that MEX-3 exhibits gel-like properties in many regards but is more dynamic than MEG-3. We find CGH-1 is dynamic but does not consistently behave liquid-like, and may be an intermediate phase within RNP granules. We also show that the distinct phases of the RNA binding proteins are associated with differential responses to stress.

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