Cik1 Targets the Minus-End Kinesin Depolymerase Kar3 to Microtubule Plus Ends

Abstract

Kar3, a Saccharomyces cerevisiae Kinesin-14, is essential for karyogamy and meiosis I but also has specific functions during vegetative growth. For its various roles, Kar3 forms a heterodimer with either Cik1 or Vik1, both of which are noncatalytic polypeptides. Here, we present the first biochemical characterization of Kar3Cik1, the kinesin motor that is essential for karyogamy. Kar3Cik1 depolymerizes microtubules from the plus end and promotes robust minus-end-directed microtubule gliding. Immunolocalization studies show that Kar3Cik1 binds preferentially to one end of the microtubule, whereas the Kar3 motor domain, in the absence of Cik1, exhibits significantly higher microtubule lattice binding. Kar3Cik1-promoted microtubule depolymerization requires ATP turnover, and the kinetics fit a single exponential function. The disassembly mechanism is not microtubule catastrophe like that induced by the MCAK Kinesin-13s. Soluble tubulin does not activate the ATPase activity of Kar3Cik1, and there is no evidence of Kar3Cik1(.)tubulin complex formation as observed for MCAK. These results reveal a novel mechanism to regulate microtubule depolymerization. We propose that Cik1 targets Kar3 to the microtubule plus end. Kar3Cik1 then uses its minus-end-directed force to depolymerize microtubules from the plus end, with each tubulin-subunit release event tightly coupled to one ATP turnover.

Ccr4 contributes to tolerance of replication stress through control ofCRT1mRNA poly(A) tail length

“…However, diverse cellular processes such as transcription, mRNA processing, spindle dynamics, and sister chromatid cohesion were also represented within the intersection dataset. Interestingly, tolerance to HU requires KAR3 and CIK1, which encode proteins that physically interact to form a minus-enddirected kinesin (Chu et al, 2005;Sproul et al, 2005), consistent with recent studies that implicate Mec1 and Rad53 in the regulation of spindle dynamics (Krishnan et al, 2004;Bachant et al, 2005). These genome-wide screens reveal that resistance to replication stress engages diverse cell regulatory processes.…”

Kinesin-14 Family Proteins HSET/XCTK2 Control Spindle Length by Cross-Linking and Sliding Microtubules

“…studies suggest that members of the Kinesin-14 family actually possess the ability to destabilize rather than to stabilize MTs (Endow et al, 1994b;Chu et al, 2005;Sproul et al, 2005). Our data showed that in human cells and in Xenopus extracts Kinesin-14 proteins promote the outward movement of the spindle poles and increase half spindle length in monopolar spindles (data not shown).…”

Perinuclear tethers license telomeric DSBs for a broad kinesin- and NPC-dependent DNA repair process

“…complex [29][30][31][32][33][34][35] . Indeed, disruption of kinesin-14 alone or in combination with Lrs4 deletion, decreased subtelomeric DSB survival to levels similar to those seen in cells deficient in cohibin or Nup84 (Fig.…”