Association between elongation factor-1? and microtubules in vivo is domain dependent and conditional

Abstract

Although the precise definition for a microtubule‐associated protein (MAP) has been the subject of debate, elongation factor‐1α (EF‐1α) fits the most basic criteria for a MAP [Durso and Cyr, 1994a]. It binds, bundles, stabilizes, and promotes the assembly of microtubules in vitro, and localizes to plant microtubule arrays in situ. In this study, the in vitro and in vivo association of EF‐1α with microtubules was further investigated. Analysis of the in vitro binding data for EF‐1α and microtubules indicates that EF‐1α binds cooperatively to the microtubule lattice. In order to investigate the interaction of EF‐1α with microtubules in vivo, GFP fusions to EF‐1α or to EF‐1α truncates were transiently expressed in living plant cells. Using this method, two putative microtubule‐binding domains on EF‐1α were identified: one in the N‐terminal domain I and one in the C‐terminal domain III. The binding of domain I to microtubules in vivo, like the binding of full‐length EF‐1α, is conditional, and requires incubation in weak, lipophilic organic acids. The binding of domain III to microtubules in vivo, however, is not conditional, and occurs under normal cellular regimes. Furthermore, domain III stabilizes cortical microtubules as determined by their resistance to the anti‐microtubule herbicide, oryzalin. Because the accumulation of EF‐1α onto microtubules is unconditional in the absence of domain I, we hypothesize that domain I negatively regulates the accumulation of EF‐1α onto microtubules in vivo. This hypothesis is discussed in terms of possible regulatory mechanisms that could affect the accumulation of EF‐1α onto microtubules within living cells. Cell Motil. Cytoskeleton 45:279–292, 2000 © 2000 Wiley‐Liss, Inc.

Eukaryotic Elongation Factor 1A Interacts with the Upstream Pseudoknot Domain in the 3′ Untranslated Region of Tobacco Mosaic Virus RNA

“…In general, protein synthesis can be enhanced by a close spatial association of the ribosome and other factors involved in translation with the cytoskeleton (2,31,57). eEF1A interacts with actin filaments, tubulin, and the ER and apparently mediates the general attachment of cellular mRNA to the cytoskeleton (2,3,13,31,45). TMV genomic RNA is associated with the plant cytoskeleton and ER throughout the infection cycle (42).…”

The resurrection plant Sporobolus stapfianus: An unlikely model for engineering enhanced plant biomass?

“…eEF1A can undergo posttranslational modifications, such as methylation and phosphorylation, and can interact with various proteins, including tubulin, calmodulin and actin. It has been suggested that eEF1A may regulate the cytoskeleton by promoting and stabilizing microtubule assembly in plants potentially in response to auxin signalling or changes in intracellular calcium levels (Moore and Cyr 2000). There is evidence that specific eEF1A isoforms, with variation in actin binding motifs, may be expressed in rapidly elongating maize tissue (Carneiro et al 1999).…”

A 90-kD Phospholipase D from Tobacco Binds to Microtubules and the Plasma Membrane

“…Elongation factor-1␣ (EF-1␣), which is involved in protein translation (Browning, 1996), binds MTs in the presence of weak lipophilic acids (Moore and Cyr, 2000) and undergoes Ca 2ϩ -mediated proteolysis in the presence of PLD␣ Tobacco BY-2 protoplasts, prepared after preincubation with 10 M taxol, were treated with calcium and detergent and then processed for immunofluorescence microscopy using double labeling with antibodies against p90 and ␣/␤-tubulin as in Figure 7. (A) and (B) Cortical MTs were removed from the protoplast ghosts by cold treatment in the presence of 5 mM CaCl 2 for 30 min.…”

“…from castor bean (Ransom-Hodgkins et al, 2000). EF-1␣ can bind, bundle, stabilize, and promote the assembly of MTs in vitro (Moore and Cyr, 2000, and references cited therein), and it also binds and bundles actin (Liu et al, 1996). Thus, EF-1␣ has the potential to be an effector of signals to both the MT and actin cytoskeletons.…”