scholarly journals TIA1 potentiates tau phase separation and promotes generation of toxic oligomeric tau

2021 ◽  
Vol 118 (9) ◽  
pp. e2014188118
Author(s):  
Peter E. A. Ash ◽  
Shuwen Lei ◽  
Jenifer Shattuck ◽  
Samantha Boudeau ◽  
Yari Carlomagno ◽  
...  
Keyword(s):  
Phase Separation ◽  
Polyethylene Glycol ◽  
Stress Response ◽  
Tau Protein ◽  
Rna Binding ◽  
Biological Activities ◽  
Rna Binding Protein ◽  
Physiological Conditions ◽  
Tau Oligomers

Tau protein plays an important role in the biology of stress granules and in the stress response of neurons, but the nature of these biochemical interactions is not known. Here we show that the interaction of tau with RNA and the RNA binding protein TIA1 is sufficient to drive phase separation of tau at physiological concentrations, without the requirement for artificial crowding agents such as polyethylene glycol (PEG). We further show that phase separation of tau in the presence of RNA and TIA1 generates abundant tau oligomers. Prior studies indicate that recombinant tau readily forms oligomers and fibrils in vitro in the presence of polyanionic agents, including RNA, but the resulting tau aggregates are not particularly toxic. We discover that tau oligomers generated during copartitioning with TIA1 are significantly more toxic than tau aggregates generated by incubation with RNA alone or phase-separated tau complexes generated by incubation with artificial crowding agents. This pathway identifies a potentially important source for generation of toxic tau oligomers in tau-related neurodegenerative diseases. Our results also reveal a general principle that phase-separated RBP droplets provide a vehicle for coassortment of selected proteins. Tau selectively copartitions with TIA1 under physiological conditions, emphasizing the importance of TIA1 for tau biology. Other RBPs, such as G3BP1, are able to copartition with tau, but this happens only in the presence of crowding agents. This type of selective mixing might provide a basis through which membraneless organelles bring together functionally relevant proteins to promote particular biological activities.

scholarly journals Low-complexity domain of U1-70K modulates phase separation and aggregation through distinctive basic-acidic motifs

2019 ◽  
Vol 5 (11) ◽  
pp. eaax5349 ◽  
Author(s):  
Song Xue ◽  
Rui Gong ◽  
Fanqi He ◽  
Yanqin Li ◽  
Yunjia Wang ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Rna Binding ◽  
Rna Binding Protein ◽  
Low Complexity ◽  
Protein Domain ◽  
Shed Light ◽  
Liquid Liquid Phase Separation

Liquid-liquid phase separation (LLPS) facilitates the formation of functional membraneless organelles and recent reports have linked this phenomenon to protein aggregation in neurodegenerative diseases. Understanding the mechanism of LLPS and its regulation thus promises to shed light on the pathogenesis of these conditions. The RNA-binding protein U1-70K, which aggregates in brains of Alzheimer’s disease patients, is considered a potential target for Alzheimer’s therapy. Here, we report that two fragments in the low-complexity (LC) domain of U1-70K can undergo LLPS. We have demonstrated that the repetitive basic-acidic motifs in these fragments induce nucleotide-independent phase separation and initiate aggregation in vitro. We also have confirmed that LLPS and aggregation occur in vivo and that the content of ampholytic motifs in a protein domain determines the transition between droplets and aggregation, providing insights into the mechanism underlying the formation of diverse assembly states.

Phase separation of RNA-binding protein promotes polymerase binding and transcription

2021 ◽  
Author(s):  
Wen Shao ◽  
Xianju Bi ◽  
Yixuan Pan ◽  
Boyang Gao ◽  
Jun Wu ◽  
...  
Keyword(s):  
Phase Separation ◽  
Rna Binding ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
Polymerase Binding

Characterization and purification of lupus antigen La, and RNA-binding protein

1985 ◽  
Vol 5 (3) ◽  
pp. 586-590
Author(s):  
A M Francoeur ◽  
E K Chan ◽  
J I Garrels ◽  
M B Mathews
Keyword(s):  
Hela Cell ◽  
Gel Electrophoresis ◽  
Rna Binding ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
In Vitro Translation ◽  
Cell Protein ◽  
Two Dimensional Gel Electrophoresis ◽  
La Antigen

HeLa cell La antigen, an RNA-binding protein, was characterized by using two-dimensional gel electrophoresis. Eight isoelectric forms (pI 6 to 7) were observed, many containing phosphate. An in vitro translation product similar in size and antigenicity was identified. The HeLa cell protein purified by using an assay based on ribonucleoprotein reconstitution with adenovirus VA RNAI also comprised several isoelectric forms.

scholarly journals The viral nucleocapsid protein and the human RNA-binding protein Mex3A promote translation of the Andes orthohantavirus small mRNA

2021 ◽  
Vol 17 (9) ◽  
pp. e1009931
Author(s):  
Jorge Vera-Otarola ◽  
Estefania Castillo-Vargas ◽  
Jenniffer Angulo ◽  
Francisco M. Barriga ◽  
Eduard Batlle ◽  
...  
Keyword(s):  
Nucleocapsid Protein ◽  
Rna Binding ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
Initiation Factor ◽  
Cellular Proteins ◽  
Dependent Manner ◽  
The Andes ◽  
Viral Nucleocapsid

The capped Small segment mRNA (SmRNA) of the Andes orthohantavirus (ANDV) lacks a poly(A) tail. In this study, we characterize the mechanism driving ANDV-SmRNA translation. Results show that the ANDV-nucleocapsid protein (ANDV-N) promotes in vitro translation from capped mRNAs without replacing eukaryotic initiation factor (eIF) 4G. Using an RNA affinity chromatography approach followed by mass spectrometry, we identify the human RNA chaperone Mex3A (hMex3A) as a SmRNA-3’UTR binding protein. Results show that hMex3A enhances SmRNA translation in a 3’UTR dependent manner, either alone or when co-expressed with the ANDV-N. The ANDV-N and hMex3A proteins do not interact in cells, but both proteins interact with eIF4G. The hMex3A–eIF4G interaction showed to be independent of ANDV-infection or ANDV-N expression. Together, our observations suggest that translation of the ANDV SmRNA is enhanced by a 5’-3’ end interaction, mediated by both viral and cellular proteins.

scholarly journals Regulation of cold-induced thermogenesis by the RNA binding protein FAM195A

2021 ◽  
Vol 118 (23) ◽  
pp. e2104650118
Author(s):  
Jessica Cannavino ◽  
Mengle Shao ◽  
Yu A. An ◽  
Svetlana Bezprozvannaya ◽  
Shiuhwei Chen ◽  
...  
Keyword(s):  
Rna Binding ◽  
Binding Protein ◽  
Uncoupling Protein ◽  
Rna Binding Protein ◽  
Cold Environments ◽  
Transport Chain ◽  
Brown Adipose ◽  
Mitochondrial Oxidation ◽  
Branched Chain

Homeothermic vertebrates produce heat in cold environments through thermogenesis, in which brown adipose tissue (BAT) increases mitochondrial oxidation along with uncoupling of the electron transport chain and activation of uncoupling protein 1 (UCP1). Although the transcription factors regulating the expression of UCP1 and nutrient oxidation genes have been extensively studied, only a few other proteins essential for BAT function have been identified. We describe the discovery of FAM195A, a BAT-enriched RNA binding protein, which is required for cold-dependent thermogenesis in mice. FAM195A knockout (KO) mice display whitening of BAT and an inability to thermoregulate. In BAT of FAM195A KO mice, enzymes involved in branched-chain amino acid (BCAA) metabolism are down-regulated, impairing their response to cold. Knockdown of FAM195A in brown adipocytes in vitro also impairs expression of leucine oxidation enzymes, revealing FAM195A to be a regulator of BCAA metabolism and a potential target for metabolic disorders.

scholarly journals Double-stranded RNA drives SARS-CoV-2 nucleocapsid protein to undergo phase separation at specific temperatures

2021 ◽  
Author(s):  
Christine Roden ◽  
Yifan Dai ◽  
Ian Seim ◽  
Myungwoon Lee ◽  
Rachel Sealfon ◽  
...  
Keyword(s):  
Phase Separation ◽  
Rna Structure ◽  
Nucleocapsid Protein ◽  
Rna Binding ◽  
Genome Packaging ◽  
Rna Motifs ◽  
Double Stranded Rna ◽  
N Protein ◽  
Binding Domains

Betacoronavirus SARS-CoV-2 infections caused the global Covid-19 pandemic. The nucleocapsid protein (N-protein) is required for multiple steps in the betacoronavirus replication cycle. SARS-CoV-2-N-protein is known to undergo liquid-liquid phase separation (LLPS) with specific RNAs at particular temperatures to form condensates. We show that N-protein recognizes at least two separate and distinct RNA motifs, both of which require double-stranded RNA (dsRNA) for LLPS. These motifs are separately recognized by N-protein's two RNA binding domains (RBDs). Addition of dsRNA accelerates and modifies N-protein LLPS in vitro and in cells and controls the temperature condensates form. The abundance of dsRNA tunes N-protein-mediated translational repression and may confer a switch from translation to genome packaging. Thus, N-protein's two RBDs interact with separate dsRNA motifs, and these interactions impart distinct droplet properties that can support multiple viral functions. These experiments demonstrate a paradigm of how RNA structure can control the properties of biomolecular condensates.

scholarly journals Heterogeneous Nuclear Ribonucleoprotein (hnRNP) E1 Binds to hnRNP A2 and Inhibits Translation of A2 Response Element mRNAs

2006 ◽  
Vol 17 (8) ◽  
pp. 3521-3533 ◽  
Author(s):  
Linda D. Kosturko ◽  
Michael J. Maggipinto ◽  
George Korza ◽  
Joo Won Lee ◽  
John H. Carson ◽  
...  
Keyword(s):  
Rna Binding ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
In Vitro Translation ◽  
Dependent Manner ◽  
Response Element ◽  
Heterogeneous Nuclear Ribonucleoprotein ◽  
Nuclear Ribonucleoprotein ◽  
Hnrnp E1

Heterogeneous nuclear ribonucleoprotein (hnRNP) A2 is a trans-acting RNA-binding protein that mediates trafficking of RNAs containing the cis-acting A2 response element (A2RE). Previous work has shown that A2RE RNAs are transported to myelin in oligodendrocytes and to dendrites in neurons. hnRNP E1 is an RNA-binding protein that regulates translation of specific mRNAs. Here, we show by yeast two-hybrid analysis, in vivo and in vitro coimmunoprecipitation, in vitro cross-linking, and fluorescence correlation spectroscopy that hnRNP E1 binds to hnRNP A2 and is recruited to A2RE RNA in an hnRNP A2-dependent manner. hnRNP E1 is colocalized with hnRNP A2 and A2RE mRNA in granules in dendrites of oligodendrocytes. Overexpression of hnRNP E1 or microinjection of exogenous hnRNP E1 in neural cells inhibits translation of A2RE mRNA, but not of non-A2RE RNA. Excess hnRNP E1 added to an in vitro translation system reduces translation efficiency of A2RE mRNA, but not of nonA2RE RNA, in an hnRNP A2-dependent manner. These results are consistent with a model where hnRNP E1 recruited to A2RE RNA granules by binding to hnRNP A2 inhibits translation of A2RE RNA during granule transport.

scholarly journals Premature Translation of oskar in Oocytes Lacking the RNA-Binding Protein Bicaudal-C

1998 ◽  
Vol 18 (8) ◽  
pp. 4855-4862 ◽  
Author(s):  
Emma E. Saffman ◽  
Sylvia Styhler ◽  
Katherine Rother ◽  
Weihua Li ◽  
Stéphane Richard ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Point Mutation ◽  
Mammalian Cells ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Rna Binding Protein ◽  
C Protein ◽  
Kh Domain ◽  
Anterior Posterior

ABSTRACT Bicaudal-C (Bic-C) is required duringDrosophila melanogaster oogenesis for several processes, including anterior-posterior patterning. The gene encodes a protein with five copies of the KH domain, a motif found in a number of RNA-binding proteins. Using antibodies raised against the BIC-C protein, we show that multiple isoforms of the protein exist in ovaries and that the protein, like the RNA, accumulates in the developing oocyte early in oogenesis. BIC-C protein expressed in mammalian cells can bind RNA in vitro, and a point mutation in one of the KH domains that causes a strong Bic-C phenotype weakens this binding. In addition, oskar translation commences prior to posterior localization of oskar RNA inBic-C − oocytes, indicating thatBic-C may regulate oskar translation during oogenesis.

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