Loss of function of the Cik1/Kar3 motor complex results in chromosomes with syntelic attachment that are sensed by the tension checkpoint.
The attachment of sister kinetochores by microtubules emanating from opposite spindle poles establishes chromosome bipolar attachment, which generates tension on chromosomes and is essential for sister-chromatid segregation. Syntelic attachment occurs when both sister kinetochores are attached by microtubules from the same spindle pole and this attachment is unable to generate tension on chromosomes, but a reliable method to induce syntelic attachments is not available in budding yeast. The spindle checkpoint can sense the lack of tension on chromosomes as well as detached kinetochores to prevent anaphase onset. In budding yeast Saccharomyces cerevisiae, tension checkpoint proteins Aurora/Ipl1 kinase and centromere-localized Sgo1 are required to sense the absence of tension but are dispensable for the checkpoint response to detached kinetochores. We have found that the loss of function of a motor protein complex Cik1/Kar3 in budding yeast leads to syntelic attachments. Inactivation of either the spindle or tension checkpoint enables premature anaphase entry in cells with dysfunctional Cik1/Kar3, resulting in co-segregation of sister chromatids. Moreover, the abolished Kar3-kinetochore interaction in cik1 mutants suggests that the Cik1/Kar3 complex mediates chromosome movement along microtubules, which could facilitate bipolar attachment. Therefore, we can induce syntelic attachments in budding yeast by inactivating the Cik1/Kar3 complex, and this approach will be very useful to study the checkpoint response to syntelic attachments.
Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, USA.
Fengzhi
F
Jin
Hong
H
Liu
Ping
P
Li
Hong-Guo
HG
Yu
Yanchang
Y
Wang
D000705:Anaphase / Q000235:genetics; D064127:Aurora Kinases; D020090:Chromosome Segregation / Q000235:genetics; D002875:Chromosomes / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D018386:Kinetochores; D059566:M Phase Cell Cycle Checkpoints / Q000235:genetics*; D008868:Microtubule Proteins / Q000235:genetics*; D008869:Microtubule-Associated Proteins / Q000235:genetics*; D008870:Microtubules / Q000235:genetics*; D008938:Mitosis / Q000235:genetics*; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D012854:Sister Chromatid Exchange / Q000235:genetics
C076025:CIK1 protein, S cerevisiae; C063504:KAR3 protein, S cerevisiae; D008868:Microtubule Proteins; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; C482640:Sgo1 protein, S cerevisiae; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases