The chromokinesin Kid (KIF22) forms a homodimer, moves processively along microtubules and transports double-stranded DNA

During prometaphase in mitosis, chromosomes are pushed toward the spindle equator. The chromokinesin Kid, also known as KIF22, moves chromosomes along spindle microtubules during prometaphase. Kid has long been considered a monomeric and non-processive motor, different from typical kinesins. In this study, we demonstrate that the full-length Kid forms a homodimer and moves processively along microtubules. A conserved coiled-coil domain within the stalk region of Kid is sufficient for homodimer formation and is required for the processivity of Kid. Furthermore, the neck linker and coiled-coil domains of Kid could add processive activity to the motor domain of KIF1A, suggesting that Kid contains a functional neck linker and dimerization capability, a prerequisite for the processivity of kinesin motor domains. The full-length Kid, containing a helix-hairpin-helix domain, can transport double-stranded DNA along microtubules in vitro. Alphafold3 prediction suggests that the dimerization of Kid stabilizes the association with DNA. These findings collectively suggest the reclassification of Kid as a processive and dimeric motor that transports DNA along microtubules.