Motor Control: How Kinesins Drive Mitosis

One of the main components of the cytoskeleton is microtubules (MTs), which are comprised of heterodimers of a- and b-tubulin proteins. Tubulin can polymerize on both ends of MTs at different rates, where polymerization occurs more rapidly on the plus-end and is slower on the minus-end. The molecular motor families, kinesins and dyneins play a role in MT length by regulating the dynamic behavior of growth and shrinkage of MTs, known as dynamic instability1. These motors work along MTs to provide cellular functions involving organelle transport, vesicle transport, meiosis, and mitosis.

Kinesins were first discovered in 1985 when it was observed that a new class of ATPases could cycle on and off microtubules and induce organelle movement along the axons of squid and vertebrate brain2,3. Since then, 45 kinesin proteins have been identified in humans, with the Kinesins superfamily (KIF) organized into 14 recognized kinesin families4. Most kinesins have a plus-end directed motility, but motors in the kinesin-14 subfamily have a C-terminal motor and are minus-end directed. The general architecture of kinesins consists of three domains: 1) a catalytic motor or head domain that is well conserved within each kinesin family that can hydrolyze ATP and binds microtubules, 2) an adjacent neck domain that is involved in coiled-coil interactions and can organize the motor into higher-order oligomers, 3) On the opposite end of the protein is the tail domain, which can be highly divergent within a kinesin family, and is sometimes used to interact with cargo proteins, DNA, or regulatory domains5–8. Below, we will look at recent findings on how kinesins affect the formation of the mitotic spindle and the organization of the chromosomes through the various stages of mitosis9.

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