Vincent Fache
Functional study of a protein associated with mitotic spindle microtubules in the model plant Arabidopsis thaliana: atMAP65-4
Published on 3 February 2011
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Thesis presented February 03, 2011
Abstract:
AtMAP65-4 is a microtubule-associated protein belonging to the AtMAP65s family that comprises 9 members identified in
Arabidopsis thaliana. These proteins belong to a family conserved during evolution, MAP65s. Thus, homologous proteins are present in mammals (PRC1), in yeast (Ase1p) or Drosophila (FEO). So far the study of molecular properties and functional AtMAP65s has focused mainly on AtMAP65-1 and AtMAP65-5. The main feature of these proteins is to induce the formation of microtubule bundles
in vitro.
In vivo, these AtMAP65s are localized with subsets of microtubule bundles as they are suggested to play a role in establishing and maintaining these networks. From the results we obtained on AtMAP65-4 properties during this work such as the in
vivo localization, biochemical properties and functional effect on the MT polymerization, we suggested that the
in vivo function of AtMAP65-4 is involved in setting up and maintaining microtubule bundles within kinetochore fibers during cell division.
In vitro studies allowed us to show that AtMAP65-4 changes the dynamic parameters of microtubule. In addition to its ability to form bundles, AtMAP65-4 allows steady growth of microtubules in bundles it induces. The mechanism of action of the MAP at the molecular level was analyzed through a bioinformatics study where we modeled the activity of AtMAP65-4 and concluded that it could block the depolymerization events. Moreover, the activity of AtMAP65-4 could be regulated
in vivo by post-translational modifications. Indeed, we have shown that AtMAP65-4 is phosphorylated by Aurora kinases
in vitro. The effect of this phosphorylation during mitosis is under investigation.
Keywords:
Microtubule associated protein, AtMAP65s,
Arabidopsis thaliana, Evanescent wave microscopy,
In silico modeling activity, Aurora kinases
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