Silencing mitosin induces misaligned chromosomes, premature chromosome decondensation before anaphase onset, and mitotic cell death.
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.
Yang
Zhenye
Z
Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People's Republic of China.
Guo
Jing
J
Chen
Qi
Q
Ding
Chong
C
Du
Juan
J
Zhu
Xueliang
X
D000705:Anaphase; D017209:Apoptosis; D002460:Cell Line; D002868:Chromosomal Proteins, Non-Histone / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D002875:Chromosomes / Q000235:genetics / Q000502:physiology*; D000072159:Dynactin Complex; D004398:Dyneins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000502:physiology; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008938:Mitosis; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D034622:RNA Interference; D008941:Spindle Apparatus / Q000473:pathology / Q000502:physiology; D013997:Time Factors
D002868:Chromosomal Proteins, Non-Histone; D000072159:Dynactin Complex; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; C068688:centromere protein E; C094772:centromere protein F; D046988:Proteasome Endopeptidase Complex; D004398:Dyneins