Feo, the Drosophila Homolog of PRC1, Is Required for Central-Spindle Formation and Cytokinesis

Abstract

We performed a functional analysis of fascetto (feo), a Drosophila gene that encodes a protein homologous to the Ase1p/PRC1/MAP65 conserved family of microtubule-associated proteins (MAPs). These MAPs are enriched at the spindle midzone in yeast and mammals and at the fragmoplast in plants, and are essential for the organization and function of these microtubule arrays. Here we show that the Feo protein is specifically enriched at the central-spindle midzone and that its depletion either by mutation or by RNAi results in aberrant central spindles. In Feo-depleted cells, late anaphases showed normal overlap of the antiparallel MTs at the cell equator, but telophases displayed thin MT bundles of uniform width instead of robust hourglass-shaped central spindles. These thin central spindles exhibited diffuse localizations of both the Pav and Asp proteins, suggesting that these spindles comprise improperly oriented MTs. Feo-depleted cells also displayed defects in the contractile apparatus that correlated with those in the central spindle; late anaphase cells formed regular contractile structures, but these structures did not constrict during telophase, leading to failures in cytokinesis. The phenotype of Feo-depleted telophases suggests that Feo interacts with the plus ends of central spindle MTs so as to maintain their precise interdigitation during anaphase-telophase MT elongation and antiparallel sliding.

Cell cycle control of spindle elongation

“…MT stabilizing CLASPs (CLIP-associated proteins, 107 ) require direct interaction with Ase1/PRC1 for their midzone localization. 108,109 In Drosophila and mammals, where PRC1 is needed for proper cytokinesis, 85,93 a number of proteins involved in cytokinesis depend on Ase1/PRC1 in their central spindle binding: Polo-like kinase 1 (Plk1), citron kinase 1 and the chromokinesins Mklp1, Mklp2 and KIF14. 96,[110][111][112] Genetic evidence suggest that many other proteins normally concentrated on the central spindle in anaphase, for example separase, the EB1 (end binding protein 1) homologue Bim1, chromosomal passenger proteins like Slk19 in yeast 88 or Aurora B kinase complex in human cells 96 require Ase1/PRC1 for this specific localization.…”

“…89,90 Cells lacking Ase1/PRC1 are unable to maintain a stable overlap between the iMTs and spindles break prematurely during anaphase B. 51,88,[91][92][93][94][95][96][97] The ability to specifically localize to and bundle iMTs in an antiparallel fashion, both in vitro and in vivo, makes Ase1/PRC1 a unique determinant of the midzone. 88,98 Moreover, unlike other midzone components, for example kinesin motor proteins and iMT plus end tracking proteins that show very dynamic behavior and transient binding to the MTs, [99][100][101][102] Ase1 is virtually immobile in the central spindle of yeast as estimated by FRAP (fluorescence recovery after photobleaching) experiments.…”

PRC 1‐labeled microtubule bundles and kinetochore pairs show one‐to‐one association in metaphase

“…Orthologs of PRC1 with conserved function include Ase1 (anaphase spindle elongation 1) in yeasts 14, 16, SPD‐1 (spindle defective 1) in Caenorhabditis elegans 17, Feo (Fascetto) in Drosophila melanogaster 18, and MAP65 (microtubule‐associated protein 65) in plants 19, all of which fall in a conserved family of non‐motor microtubule‐associated proteins (MAPs).…”

Two Microtubule-associated Proteins of Arabidopsis MAP65s Promote Antiparallel Microtubule Bundling

“…They are mainly members of the MT-associated family MAP65s (Smertenko et al, 2004;Wicker-Planquart et al, 2004;Li et al, 2007a). MAP65 proteins are evolutionarily conserved, nonmotor microtubule-associated proteins (MAPs) that in animal and yeast cells accumulate in the spindle midzone during late anaphase to stabilize overlapping antiparallel arranged MTs (Verni et al, 2004;Zhu et al, 2006;Janson et al, 2007). In Arabidopsis nine AtMAP65 family members were identified (Hussey et al, 2002).…”

“…In Arabidopsis nine AtMAP65 family members were identified (Hussey et al, 2002). These all possess a conserved sequence of 16 amino acids located at the C-terminus and coiled-coil sequences with putative protein-protein interaction activity (Schuyler et al, 2003;Verni et al, 2004). Overall sequence identity is poorly conserved, suggesting that AtMAP65 proteins have adopted separate properties.…”