ASH1 mRNA Anchoring Requires Reorganization of the Myo4p-She3p-She2p Transport Complex

Gonsalvez, Graydon B.; Little, Jaime L.; Long, Roy

doi:10.1074/jbc.m406086200

Cited by 21 publications

(21 citation statements)

References 42 publications

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“…This corresponds to the reduction observed in HeLa cells transfected with siRNA oligonucleotides targeting myosin Va. Given the established role that myosin Va plays in the transport of mRNP complexes in a number of model systems (10,11,26), our data suggests that myosin Va is involved in the targeting of mRNA to P bodies, or the sites of P body nucleation, for storage and/or degradation.…”

Section: Myosin Va Is Necessary For Pb Assembly-examination Of the Insupporting

confidence: 74%

Myosin Va Is Required for P Body but Not Stress Granule Formation

Lindsay

McCaffrey

2011

Journal of Biological Chemistry

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In the present study we demonstrate an association between mammalian myosin Va and cytoplasmic P bodies, microscopic ribonucleoprotein granules that contain components of the 5-3 mRNA degradation machinery. Myosin Va colocalizes with several P body markers and its RNAi-mediated knockdown results in the disassembly of P bodies. Overexpression of a dominant-negative mutant of myosin Va reduced the motility of P bodies in living cells. Co-immunoprecipitation experiments demonstrate that myosin Va physically associates with eIF4E, an mRNA binding protein that localizes to P bodies. In contrast, we find that myosin Va does not play a role in stress granule formation. Stress granules are ribonucleoprotein structures that are involved in translational silencing and are spatially, functionally, and compositionally linked to P bodies. Myosin Va is found adjacent to stress granules in stressed cells but displays minimal localization within stress granules, and myosin Va knockdown has no effect on stress granule assembly or disassembly. Combined with recently published reports demonstrating a role for Drosophila and mammalian class V myosins in mRNA transport and the involvement of the yeast myosin V orthologue Myo2p in P body assembly, our results provide further evidence that the class V myosins serve an important role in the transport and turnover of mRNA.Class V myosins are actin-based motor proteins composed of two identical heavy chains and several associated light chains. The amino-terminal head domain binds to ATP and actin filaments and provides the motive force for the complex. The neck region contains six calmodulin binding IQ motifs and acts as a lever arm, whereas the carboxyl-terminal tail domain mediates binding to cargo (1). Yeast have two class V myosins, flies and worms have one, whereas mammals have three (Va, Vb, and Vc). Myosin Va (MyoVa) 2 is widely expressed but is enriched in brain, testes, and skin. It has been implicated in a diverse range of cellular roles, including synaptic vesicle transport (2), insulin secretion (3), myelination (4), and long term potentiation (5). People who lack functional myosin Va suffer from a rare autosomal recessive disorder called Griscelli syndrome, which is characterized by hypopigmentation and severe neurological defects (6).It is well established that the yeast class V myosin Myo4p actively transports Ash1 mRNA to the bud tip of dividing cells (7), but it is now emerging that class V myosins from higher eukaryotes also play roles in RNA transport. Myosin Va has been found associated with several RNA binding proteins in a messenger ribonucleoprotein (mRNP) complex precipitated from a mouse brain extract (8). The intracellular distribution of RNA is dramatically altered in primary cells derived from dilute-lethal (myosin Va-null) mice (9). Yoshimura et al. (10) have shown that myosin Va mediates the translocation of TLS (translated in liposarcoma) and its target RNA, Nd1-L, into dendritic spines, and myosin V is involved in targeting oskar mRNA to the posterior po...

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Section: Myosin Va Is Necessary For Pb Assembly-examination Of the Insupporting

confidence: 74%

Myosin Va Is Required for P Body but Not Stress Granule Formation

Lindsay

McCaffrey

2011

Journal of Biological Chemistry

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“…RNP remodeling during events such as transcription, nuclear export, and degradation have been well documented (reviewed in references 24 and 30), but little is known about remodeling during RNA localization. In Saccharomyces cerevisiae, rearrangement of the ASH1 mRNA localization complex is required for anchoring of the RNA at its destination (14). Certain RNA helicases are required for proper localization and translational regulation of oskar mRNA (33,34), hinting at a role for remodeling during RNA localization in the Drosophila oocyte.…”

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confidence: 99%

PTB/hnRNP I Is Required for RNP Remodeling during RNA Localization in Xenopus Oocytes

Lewis

Gagnon

Mowry

2008

Molecular and Cellular Biology

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Transport of specific mRNAs to defined regions within the cell cytoplasm is a fundamental mechanism for regulating cell and developmental polarity. In the Xenopus oocyte, Vg1 RNA is transported to the vegetal cytoplasm, where localized expression of the encoded protein is critical for embryonic polarity. The Vg1 localization pathway is directed by interactions between key motifs within Vg1 RNA and protein factors recognizing those RNA sequences. We have investigated how RNA-protein interactions could be modulated to trigger distinct steps in the localization pathway and found that the Vg1 RNP is remodeled during cytoplasmic RNA transport. Our results implicate two RNA-binding proteins with key roles in Vg1 RNA localization, PTB/hnRNP I and Vg1RBP/vera, in this process. We show that PTB/hnRNP I is required for remodeling of the interaction between Vg1 RNA and Vg1RBP/vera. Critically, mutations that block this remodeling event also eliminate vegetal localization of the RNA, suggesting that RNP remodeling is required for localization.

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“…In any event, our results clearly show that She3p-S348E and She3p-S343E S361E are defective for ASH1 mRNA localization through a novel activity, since these mutants retain the ability to associate with Myo4p and She2p. Previously, we demonstrated that a reporter mRNA artificially tethered to She2p could not localize in a manner analogous to ASH1 mRNA, and these results implied that mRNA artificially tethered to She2p could not properly anchor at the bud tip (24). From these results we hypothesized that a molecular reorganization event occurs that releases She2p from the Myo4p-She3p-ASH1 mRNA anchoring complex.…”

Section: Vol 8 2009mentioning

confidence: 89%

“…The N terminus of She3p has the ability to associate with the type V myosin, Myo4p (7,19,47). Furthermore, She3p can simultaneously associate with Myo4p and the She2p-ASH1 mRNA complex (21,24). These observations led to the current model for ASH1 mRNA localization in which the simultaneous association of She3p with Myo4p and the She2p-ASH1 mRNA complex results in the formation of a transport particle that moves along the polarized actin cytoskeleton into the daughter cell (7,41,63).…”

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confidence: 98%

She3p Possesses a Novel Activity Required for ASH1 mRNA Localization in Saccharomyces cerevisiae

et al. 2009

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Intracellular and intercellular polarity requires that specific proteins be sorted to discreet locations within and between cells. One mechanism for sorting proteins is through RNA localization. In Saccharomyces cerevisiae, ASH1 mRNA localizes to the distal tip of the bud, resulting in the asymmetric sorting of the transcriptional repressor Ash1p. ASH1 mRNA localization requires four cis-acting localization elements and the trans-acting factors Myo4p, She3p, and She2p. Myo4p is a type V myosin motor that functions to directly transport ASH1 mRNA to the bud. She2p is an RNA-binding protein that directly interacts with the ASH1 mRNA cis-acting elements. Currently, the role for She3p in ASH1 mRNA localization is as an adaptor protein, since it can simultaneously associate with Myo4p and She2p. Here, we present data for two novel mutants of She3p, S348E and the double mutant S343E S361E, that are defective for ASH1 mRNA localization, and yet both of these mutants retain the ability to associate with Myo4p and She2p. These observations suggest that She3p possesses a novel activity required for ASH1 mRNA localization, and our data imply that this function is related to the ability of She3p to associate with ASH1 mRNA. Interestingly, we determined that She3p is phosphorylated, and global mass spectrometry approaches have determined that Ser 343, 348, and 361 are sites of phosphorylation, suggesting that the novel function for She3p could be negatively regulated by phosphorylation. The present study reveals that the current accepted model for ASH1 mRNA localization does not fully account for the function of She3p in ASH1 mRNA localization.RNA localization is a process to spatially and temporally restrict intracellular and intercellular protein expression. This mechanism for protein sorting is utilized by a number of eukaryotic organisms including mammals, Drosophila melanogaster, Xenopus spp., and Saccharomyces cerevisiae (4,15,25,37,44). RNA localization can be achieved through at least three distinct mechanisms: cytoplasmic diffusion followed by entrapment of the RNA at the site of localization, generalized degradation/localized protection, and directed transport using motor proteins and cytoskeletal elements (60). S. cerevisiae utilizes directed transport to localize at least 30 mRNAs to the bud tip (2,3,57,61). Localization of ASH1 mRNA to the bud tip in yeast results in the asymmetric sorting of Ash1p to the daughter cell nucleus (10,43,62). Ash1p is a transcriptional repressor that prevents expression of the HO endonuclease in the daughter cell, restricting mating-type switching exclusively to the mother cell (6,36,45,58).ASH1 mRNA localization is dependent on She2p, She3p, and Myo4p (43, 62). She2p is an RNA-binding protein that associates with the four ASH1 mRNA cis-acting localization elements: E1, E2A, E2B, and E3 (7,11,26,41,48). She2p also directly associates with the C terminus of She3p (7,11,26,41,48). The N terminus of She3p has the ability to associate with the type V myosin, Myo4p (7,19,47). Furthermore...

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ASH1 mRNA Anchoring Requires Reorganization of the Myo4p-She3p-She2p Transport Complex

Cited by 21 publications

References 42 publications

Myosin Va Is Required for P Body but Not Stress Granule Formation

Myosin Va Is Required for P Body but Not Stress Granule Formation

PTB/hnRNP I Is Required for RNP Remodeling during RNA Localization in Xenopus Oocytes

She3p Possesses a Novel Activity Required for ASH1 mRNA Localization in Saccharomyces cerevisiae

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