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Molecular and Cellular Biology, May 2005, p. 4062-4074, Vol. 25, No. 10
0270-7306/05/$08.00+0     doi:10.1128/MCB.25.10.4062-4074.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Silencing Mitosin Induces Misaligned Chromosomes, Premature Chromosome Decondensation before Anaphase Onset, and Mitotic Cell Death{dagger}

Zhenye Yang,{ddagger} Jing Guo,{ddagger} Qi Chen, Chong Ding, Juan Du, and Xueliang Zhu*

Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People's Republic of China

Received 3 September 2004/ Returned for modification 13 October 2004/ Accepted 8 February 2005

Mitosin (also named CENP-F) is a large human nuclear protein transiently associated with the outer kinetochore plate in M phase. Using RNA interference and fluorescence microscopy, we showed that mitosin depletion attenuated chromosome congression and led to metaphase arrest with misaligned polar chromosomes whose kinetochores showed few cold-stable microtubules. Kinetochores of fully aligned chromosomes often failed to show orientation in the direction of the spindle long axis. Moreover, tension across their sister kinetochores was decreased by 53% on average. These phenotypes collectively imply defects in motor functions in mitosin-depleted cells and are similar to those of CENP-E depletion. Consistently, the intensities of CENP-E and cytoplasmic dynein and dynactin, which are motors controlling microtubule attachment and chromosome movement, were reduced at the kinetochore in a microtubule-dependent manner. In addition, after being arrested in pseudometaphase for approximately 2 h, mitosin-depleted cells died before anaphase initiation through apoptosis. The dying cells exhibited progressive chromosome arm decondensation, while the centromeres were still associated with spindles. Mitosin is therefore essential for full chromosome alignment, possibly by promoting proper kinetochore attachments through modulating CENP-E and dynein functions. Its depletion also prematurely triggers chromosome decondensation, a process that normally occurs from telophase for the nucleus reassembly, thus resulting in apoptosis.

* Corresponding author. Mailing address: Institute of Biochemistry and Cell Biology, 320 Yue Yang Road, Shanghai 200031, People's Republic of China. Phone: 86-21-54921406. Fax: 86-21-54921011. E-mail: xlzhu{at}sibs.ac.cn.

{dagger} Supplemental material for this article may be found at http://mcb.asm.org.

{ddagger} These authors contributed equally to this work.

Molecular and Cellular Biology, May 2005, p. 4062-4074, Vol. 25, No. 10
0022-538X/05/$08.00+0     doi:10.1128/MCB.25.10.4062-4074.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



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