Function of the p86 subunit of eukaryotic initiation factor (iso)4F as a microtubule-associated protein in plant cells.

Bokros, Carol L.; Hugdahl, Jeffrey D.; Kim, Hyong-Ha; Hanesworth, Virginia R.; Heerden, Ann van; Browning, Karen S.; Morejohn, Louis C.

doi:10.1073/pnas.92.15.7120

Cited by 48 publications

(48 citation statements)

References 46 publications

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“…1C) and LC-MS/MS (Table III), EF-1␣ (spot 38) was an abundant protein in the tubulin-binding protein fraction. Several other elongation and initiation factors were also identified, some of which have been shown to bind to MTs and other cytoskeletal structures in previous studies (Table III) (12,(43)(44)(45)(46). These included EF-2 (spot 4) and subunits of the eukaryotic translation initiation factors eIF3 and eIF4 (spots 7,18,24,27,50,54,70).…”

Section: Resultsmentioning

confidence: 99%

Large-scale Identification of Tubulin-binding Proteins Provides Insight on Subcellular Trafficking, Metabolic Channeling, and Signaling in Plant Cells

Chuong

Good

Taylor

et al. 2004

Molecular & Cellular Proteomics

115

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Microtubules play an essential role in the growth and development of plants and are known to be involved in regulating many cellular processes ranging from translation to signaling. In this article, we describe the proteomic characterization of Arabidopsis tubulin-binding proteins that were purified using tubulin affinity chromatography. Microtubule co-sedimentation assays indicated that most, if not all, of the proteins in the tubulin-binding protein fraction possessed microtubule-binding activity. Two-dimensional gel electrophoresis of the tubulin-binding protein fraction was performed, and 86 protein spots were excised and analyzed for protein identification. A total of 122 proteins were identified with high confidence using LC-MS/MS. These proteins were grouped into six categories based on their predicted functions: microtubule-associated proteins, translation factors, RNA-binding proteins, signaling proteins, metabolic enzymes, and proteins with other functions. Almost one-half of the proteins identified in this fraction were related to proteins that have previously been reported to interact with microtubules. This study represents the first large-scale proteomic identification of eukaryotic cytoskeleton-binding proteins, and provides insight on subcellular trafficking, metabolic channeling, and signaling in plant cells. Molecular & Cellular Proteomics 3:970 -983, 2004.The cytoskeleton is the single most important structure that contributes to the highly ordered organization of the eukaryotic cell. It provides a framework for cell division and the trafficking of organelles and macromolecules, and also serves to regulate important cellular processes such as signaling, translation, and metabolism. The cytoskeleton plays a key role in a number of plant-specific processes, such as assisting in the formation of the cell plate, regulating cell-to-cell movement, and influencing the direction of cell elongation (1). A role for the microtubule (MT) 1 component of the cytoskeleton in many of these processes has been demonstrated, and a number of MT-binding proteins that are responsible for regulating these events have been identified.Plant MTs are assembled into four distinct arrays during the cell cycle (2). Three of these arrays-the interphase cortical array, the pre-prophase band, and the phragmoplast-have no counterpart in animal cells. The cortical MT array has been linked to the regulation of cellulose microfibril deposition and, hence, a role in cell expansion, while the pre-prophase band and the phragmoplast have important roles in the positioning and synthesis of the new cell plate in dividing cells. The fourth array, the spindle, has an evolutionarily conserved role in the segregation of chromosomes during cell division. The organization and dynamics of MTs in these arrays depend on the activity of various MT-associated proteins (MAPs). Several plant MAPs have been identified, including the 65-kDa MAPs, MAP 190, and MOR1 (3). These proteins are important in cross-bridging MTs, linking MTs with actin filamen...

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Section: Resultsmentioning

confidence: 99%

Large-scale Identification of Tubulin-binding Proteins Provides Insight on Subcellular Trafficking, Metabolic Channeling, and Signaling in Plant Cells

Chuong

Good

Taylor

et al. 2004

Molecular & Cellular Proteomics

115

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“…The putative tobacco subunit of the transcription and mRNA export factor complex, THO2, whose Arabidopsis ortholog (At1g24706) was highly enriched in our MAP preparations (Supplemental Table S1), was shown to directly bind MTs in vitro and to decorate cortical MTs in tobacco BY-2 cells . Eukaryotic elongation factors EF-1a and EF-4F exhibit the biochemical properties of MAPs (Bokros et al, 1995;Moore and Cyr, 2000) and are enriched in our MAP preparations. Recent studies suggest that a large fraction of mRNAs are localized to subcellular compartments in polarized, asymmetric cells by mechanisms that involve the transport of RNA granules by molecular motors along the MT and actin cytoskeletons and result in spatially and temporally regulated translation (Martin and Ephrussi, 2009).…”

Section: Analysis and Assessment Of Map-enriched Preparations By Lc-mmentioning

confidence: 99%

Purification and Characterization of Novel Microtubule-Associated Proteins from Arabidopsis Cell Suspension Cultures

Hamada¹,

Nagasaki-Takeuchi²,

Kato³

et al. 2013

Plant Physiology

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Plant microtubules (MTs) play essential roles in cell division, anisotropic cell expansion, and overall organ morphology. Microtubule-associated proteins (MAPs) bind to MTs and regulate their dynamics, stability, and organization. Identifying the full set of MAPs in plants would greatly enhance our understanding of how diverse MT arrays are formed and function; however, few proteomics studies have characterized plant MAPs. Using liquid chromatography-tandem mass spectrometry, we identified hundreds of proteins from MAP-enriched preparations derived from cell suspension cultures of Arabidopsis (Arabidopsis thaliana). Previously reported MAPs, MT regulators, kinesins, dynamins, peroxisome-resident enzymes, and proteins implicated in replication, transcription, and translation were highly enriched. Dozens of proteins of unknown function were identified, among which 12 were tagged with green fluorescent protein (GFP) and examined for their ability to colocalize with MTs when transiently expressed in plant cells. Six proteins did indeed colocalize with cortical MTs in planta. We further characterized one of these MAPs, designated as BASIC PROLINE-RICH PROTEIN1 (BPP1), which belongs to a sevenmember family in Arabidopsis. BPP1-GFP decorated interphase and mitotic MT arrays in transgenic Arabidopsis plants. A highly basic, conserved region was responsible for the in vivo MT association. Overexpression of BPP1-GFP stabilized MTs, caused right-handed helical growth in rapidly elongating tissues, promoted the formation of transverse MT arrays, and resulted in the outgrowth of epidermal cells in light-grown hypocotyls. Our high-quality proteome database of Arabidopsis MAP-enriched preparations is a useful resource for identifying novel MT regulators and evaluating potential MT associations of proteins known to have other cellular functions.Microtubules (MTs) are major structural components of the plant cytoskeleton that are composed of a-tubulin/b-tubulin heterodimer subunits and are intricately involved in cell division, morphology, and intracellular organization and transport. The ability of the MT cytoskeleton to fulfill its versatile cellular functions relies on its intrinsically dynamic polymer properties. Individual MTs alternate between phases of growth and shrinkage by rapidly attaching and removing tubulin subunits at their ends. These cycles of polymerization and depolymerization, which continuously reorganize the MT cytoskeleton, are sometimes interrupted by pauses in which neither growth nor shrinkage occurs (Desai and Mitchison,

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“…Additional functions for eIFiso4G have also been reported. eIFiso4G was shown to bind, bundle and co-localize with microtubules in maize cells (18), and to promote their growth by end-to-end annealing in vitro (24), suggesting possible roles for eIFiso4F in the localization of translational components to the cytoskeleton (18) or in mRNA transport (1). These relatively ancient RNA-binding proteins may therefore have other functions in both the nucleus and cytoplasm, beyond formation of the 43 S preinitiation complex in translation.…”

Section: Table II Nucleic Acid Binding Specificity Of Eifiso4f and Thmentioning

confidence: 99%

“…The N-terminal region of eIFiso4G appears to bind poly(A)-binding protein (17), thereby increasing its activity. Additionally, recombinant wheat eIFiso4G binds to, and promotes the bundling of microtubules in vitro, and co-localizes with microtubules in vivo, suggesting a role for eIFiso4F in localizing the translational machinery to the cytoskeleton (18). The specific sites and structural motifs in eIFiso4G or eIF4G that mediate most of these RNA and protein interactions have not yet been identified.…”

mentioning

confidence: 99%

Identification of a Nucleic Acid Binding Domain in Eukaryotic Initiation Factor eIFiso4G from Wheat

Kim¹,

Takahashi²,

Nguyen³

et al. 1999

Journal of Biological Chemistry

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Higher plants have two complexes that bind the m 7 Gcap structure of mRNA and mediate interactions between mRNA and ribosomal subunits, designated eIF4F and eIFiso4F. Both complexes contain a small subunit that binds the 5-cap structure of mRNA, and a large subunit, eIF4G or eIFiso4G, that binds other translation factors and RNA. Sequence-specific proteases were used to cleave native cap-binding complexes into structural domains, which were purified by affinity chromatography. We show here that eIFiso4G contains a central pro- The group 4 translation initiation factors, eIF4A, 1 B, E, and G, bind and recruit mRNA to 43 S pre-initiation complexes for translation (reviewed in Refs. 1 and 2). Association of eIF4A and eIF4B confers ATPase, RNA helicase, and RNA annealing activities on the intact complex (1-3) and is thought to be necessary for melting of RNA secondary structure and ribosome scanning to the AUG start codon. eIF4E binds to the 5Ј-cap structure of mRNAs and associates tightly with eIF4G. These two factors together form the core of the mRNA-binding complex, designated eIF4F. Higher plants have two such complexes: eIF4F, which is homologous to the mammalian complex, and eIFiso4F, which is ϳ10-fold more abundant (4, 5). eIF4G and eIFiso4G differ ϳ2-fold in molecular mass and show only 25-30% sequence similarity overall, with ϳ50% similarity in six small homologous regions (6). Yet, despite this substantial divergence, these two factors have very similar functions (1). Either factor alone is sufficient for cap-dependent initiation in vitro (7,8). eIFiso4G and eIFiso4E have been cloned and sequenced from wheat and have deduced molecular masses of 86.5 and 23.5 kDa, respectively (6).The eIF4G and eIFiso4G subunits of the mRNA-binding complexes act as a central scaffold for binding of other translation factors, proteins, co-factors, and RNAs. These include binding sites within mammalian eIF4G for eIF4E (aa 409 -457) (9), eIF3 (aa 480 -886) (10), and two sites for eIF4A (aa 887-1402 and 478 -883) (10, 11). Plant eIFiso4G also binds eIFiso4E near its N terminus (aa 52-90) (12) in a small region with sequence homology to the mammalian factor. Binding of eIF4G and eIFiso4G to RNAs, distinct from the cap recognition function of the intact complex, has been demonstrated by several laboratories and appears to play a critical role in the cap-independent initiation of viral RNAs. Sha et al. (13) calculated the equilibrium binding constants of recombinant wheat eIFiso4G for both capped and uncapped mRNAs. They found that the binding constants for uncapped message were comparable to those of eIFiso4E and eIFiso4F for capped mRNA, clearly indicating that the large subunit also binds mRNA efficiently and that it does not discriminate between capped and uncapped messages. These findings are consistent with the role of eIF4G in the cap-independent translation of viral mRNAs, following cleavage and loss of the eIF4E binding domain by viral proteases (10, 14). In functional assays for initiation complex formation, Pestova et...

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Function of the p86 subunit of eukaryotic initiation factor (iso)4F as a microtubule-associated protein in plant cells.

Cited by 48 publications

References 46 publications

Large-scale Identification of Tubulin-binding Proteins Provides Insight on Subcellular Trafficking, Metabolic Channeling, and Signaling in Plant Cells

Large-scale Identification of Tubulin-binding Proteins Provides Insight on Subcellular Trafficking, Metabolic Channeling, and Signaling in Plant Cells

Purification and Characterization of Novel Microtubule-Associated Proteins from Arabidopsis Cell Suspension Cultures

Identification of a Nucleic Acid Binding Domain in Eukaryotic Initiation Factor eIFiso4G from Wheat

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