Regulation of Microtubule Dynamics by Bim1 and Bik1, the Budding Yeast Members of the EB1 and CLIP-170 Families of Plus-End Tracking Proteins

Blake-Hodek, Kristina; Cassimeris, Lynne; Huffaker, Tim C.

doi:10.1091/mbc.e10-02-0083

Cited by 49 publications

(47 citation statements)

References 63 publications

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“…homodimers that interact to create a tetramer that in turn binds microtubule plus ends (Blake-Hodek et al 2010). Combinatorial interactions among the different MAPS provide a mechanism to increase the number of distinct activities from a limited number of proteins.…”

Section: Microtubule-associated Proteinsmentioning

confidence: 99%

Mitotic Spindle Form and Function

2012

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The Saccharomyces cerevisiae mitotic spindle in budding yeast is exemplified by its simplicity and elegance. Microtubules are nucleated from a crystalline array of proteins organized in the nuclear envelope, known as the spindle pole body in yeast (analogous to the centrosome in larger eukaryotes). The spindle has two classes of nuclear microtubules: kinetochore microtubules and interpolar microtubules. One kinetochore microtubule attaches to a single centromere on each chromosome, while approximately four interpolar microtubules emanate from each pole and interdigitate with interpolar microtubules from the opposite spindle to provide stability to the bipolar spindle. On the cytoplasmic face, two to three microtubules extend from the spindle pole toward the cell cortex. Processes requiring microtubule function are limited to spindles in mitosis and to spindle orientation and nuclear positioning in the cytoplasm. Microtubule function is regulated in large part via products of the 6 kinesin gene family and the 1 cytoplasmic dynein gene. A single bipolar kinesin (Cin8, class Kin-5), together with a depolymerase (Kip3, class Kin-8) or minus-end-directed kinesin (Kar3, class Kin-14), can support spindle function and cell viability. The remarkable feature of yeast cells is that they can survive with microtubules and genes for just two motor proteins, thus providing an unparalleled system to dissect microtubule and motor function within the spindle machine.

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Section: Microtubule-associated Proteinsmentioning

confidence: 99%

Mitotic Spindle Form and Function

2012

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“…End-binding proteins recognize a tubulin conformation unique to the growing ends of MTs and can affect the dynamics of plusends by intrinsically altering the structure of the MT end (6)(7)(8) as well as recruiting other interacting proteins (9). In contrast, TOG domain-containing proteins, such as XMAP215, promote MT growth and have been suggested to act as MT "polymerases" (10,11).…”

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confidence: 99%

Regulation of microtubule minus-end dynamics by CAMSAPs and Patronin

Hendershott

Vale

2014

Proc. Natl. Acad. Sci. U.S.A.

157

184

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The microtubule (MT) cytoskeleton plays an essential role in mitosis, intracellular transport, cell shape, and cell migration. The assembly and disassembly of MTs, which can occur through the addition or loss of subunits at the plus-or minus-ends of the polymer, is essential for MTs to carry out their biological functions. A variety of proteins act on MT ends to regulate their dynamics, including a recently described family of MT minus-end binding proteins called calmodulin-regulated spectrin-associated protein (CAMSAP)/Patronin/Nezha. Patronin, the single member of this family in Drosophila, was previously shown to stabilize MT minusends against depolymerization in vitro and in vivo. Here, we show that all three mammalian CAMSAP family members also bind specifically to MT minus-ends and protect them against kinesin-13-induced depolymerization. However, these proteins differ in their abilities to suppress tubulin addition at minus-ends and to dissociate from MTs. CAMSAP1 does not interfere with polymerization and tracks along growing minus-ends. CAMSAP2 and CAMSAP3 decrease the rate of tubulin incorporation and remain bound, thereby creating stretches of decorated MT minus-ends. By using truncation analysis, we find that somewhat different minimal domains of CAMSAP and Patronin are involved in minus-end localization. However, we find that, in both cases, a highly conserved C-terminal domain and a more variable central domain cooperate to suppress minus-end dynamics in vitro and that both regions are required to stabilize minus-ends in Drosophila S2 cells. These results show that members of the CAMSAP/Patronin family all localize to and protect minus-ends but have evolved distinct effects on MT dynamics.tubulin polymerization | cytoskeletal regulation | TIRF microscopy M icrotubules (MTs) are cellular polymers that are important for a variety of functions, including cargo transport and mitotic spindle formation. MTs are composed of dimers of α-and β-tubulin that assemble head-to-tail, creating a polar protofilament. Protofilaments then assemble laterally to form the canonical 13-protofilament MT structure, with β-tubulin exposed at fast-growing plus-ends and α-tubulin exposed at slow-growing minus-ends (1). MTs exhibit an intriguing property termed "dynamic instability," whereby the polymer can abruptly switch between episodes of net growth and shrinkage (2). The rates of growth and shrinkage as well as the frequency of transitions between these two states are regulated by numerous MT-associated proteins, many of which bind to the ends of the polymer (3, 4).The dynamics of MT plus-ends are regulated by a well-characterized network of plus-end tracking proteins (+TIPs) (5). End-binding proteins recognize a tubulin conformation unique to the growing ends of MTs and can affect the dynamics of plusends by intrinsically altering the structure of the MT end (6-8) as well as recruiting other interacting proteins (9). In contrast, TOG domain-containing proteins, such as XMAP215, promote MT growth and have been suggested ...

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“…The diverse functions of MTs are made possible through the action of motors (i.e., kinesin and dynein) and nonmotor MT-associated proteins (MAPs) that tightly regulate the MT network. Some of these proteins act by binding directly to the ends of MTs, either to the highly dynamic plus end, such as the conserved end-binding proteins (9,10), or to the minus end (11,12). Other MT regulators, such as MAP1 and MAP2/Tau, bind along the MT lattice, stabilizing it and helping build parallel arrays, most notably in axons (13,14).…”

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confidence: 99%

Near-atomic cryo-EM structure of PRC1 bound to the microtubule

Kellogg

Howes

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Proteins that associate with microtubules (MTs) are crucial to generate MT arrays and establish different cellular architectures. One example is PRC1 (protein regulator of cytokinesis 1), which cross-links antiparallel MTs and is essential for the completion of mitosis and cytokinesis. Here we describe a 4-Å-resolution cryo-EM structure of monomeric PRC1 bound to MTs. Residues in the spectrin domain of PRC1 contacting the MT are highly conserved and interact with the same pocket recognized by kinesin. We additionally found that PRC1 promotes MT assembly even in the presence of the MT stabilizer taxol. Interestingly, the angle of the spectrin domain on the MT surface corresponds to the previously observed cross-bridge angle between MTs cross-linked by full-length, dimeric PRC1. This finding, together with molecular dynamic simulations describing the intrinsic flexibility of PRC1, suggests that the MT-spectrin domain interface determines the geometry of the MT arrays cross-linked by PRC1.ells rely on the microtubule (MT) cytoskeleton to help organize organelles (1), control cellular morphology (2), provide mechanical stability (3, 4), and form the spindle apparatus used to segregate chromosomes during cell division (5-8). The diverse functions of MTs are made possible through the action of motors (i.e., kinesin and dynein) and nonmotor MT-associated proteins (MAPs) that tightly regulate the MT network. Some of these proteins act by binding directly to the ends of MTs, either to the highly dynamic plus end, such as the conserved end-binding proteins (9, 10), or to the minus end (11,12). Other MT regulators, such as MAP1 and MAP2/Tau, bind along the MT lattice, stabilizing it and helping build parallel arrays, most notably in axons (13,14). Members of the MAP65 family, which includes human protein regular of cytokinesis 1 (PRC1) and its budding yeast ortholog Ase1, form antiparallel MT arrays important for setting the spindle midzone and determining the location of the cytokinetic ring (8,(15)(16)(17)(18)(19). In addition to binding selectively to antiparallel MTs, PRC1 recruits other spindle-organizing factors and therefore is an essential component of the mitotic spindle (15,20). Proper functioning of PRC1 requires cell-cycle-dependent localization and regulation. PRC1 contains two nuclear localization signals (NLSs) in its C-terminal domain (Fig. 1A) and is found almost exclusively in the nucleus during interphase (21-23). As the cell enters mitosis, PRC1 localizes to the spindle and becomes concentrated at the midzone by late anaphase (22), similar to observations for Ase1 (24). PRC1 is subject to phosphorylation by several cyclin-cyclin-dependent kinase (CDK) complexes (21) and together with kinesin-4 can regulate MT antiparallel overlap at the spindle midzone (20,23,25,26).Previous studies have identified that the dimerization domain of PRC1 is within the N-terminal domain (Fig. 1A) and that the primary MT binding region relies on a set of conserved residues within the central spectrin domain (PRC1-S) (15,22,2...

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Regulation of Microtubule Dynamics by Bim1 and Bik1, the Budding Yeast Members of the EB1 and CLIP-170 Families of Plus-End Tracking Proteins

Cited by 49 publications

References 63 publications

Mitotic Spindle Form and Function

Mitotic Spindle Form and Function

Regulation of microtubule minus-end dynamics by CAMSAPs and Patronin

Near-atomic cryo-EM structure of PRC1 bound to the microtubule

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