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J Cell Sci. 2018 Mar 22;131(6). pii: jcs212092. doi: 10.1242/jcs.212092.

Ki-67 and condensins support the integrity of mitotic chromosomes through distinct mechanisms.

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Cellular Dynamics Laboratory, RIKEN, Wako 351-0198, Japan
Chromosome Dynamics Laboratory, RIKEN, Wako 351-0198, Japan.
Division of Molecular Cell Engineering, NIG, Mishima 411-8540, Japan.
Department of Medical Cell Biology, IMEG, Kumamoto University, Kumamoto 860-0811, Japan.
Department of Cancer Biology, The Cancer Institute of JFCR, Tokyo 135-8550, Japan.
Cellular Dynamics Laboratory, RIKEN, Wako 351-0198, Japan.


Although condensins play essential roles in mitotic chromosome assembly, Ki-67 (also known as MKI67), a protein localizing to the periphery of mitotic chromosomes, had also been shown to make a contribution to the process. To examine their respective roles, we generated a set of HCT116-based cell lines expressing Ki-67 and/or condensin subunits that were fused with an auxin-inducible degron for their conditional degradation. Both the localization and the dynamic behavior of Ki-67 on mitotic chromosomes were not largely affected upon depletion of condensin subunits, and vice versa. When both Ki-67 and SMC2 (a core subunit of condensins) were depleted, ball-like chromosome clusters with no sign of discernible thread-like structures were observed. This severe defective phenotype was distinct from that observed in cells depleted of either Ki-67 or SMC2 alone. Our results show that Ki-67 and condensins, which localize to the external surface and the central axis of mitotic chromosomes, respectively, have independent yet cooperative functions in supporting the structural integrity of mitotic chromosomes.


AID; Auxin-inducible degron; Condensin; Ki-67; Mitotic chromosome

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Conflict of interest statement

Competing interestsThe authors declare no competing or financial interests.

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