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

• Published in: Journal of cell science Vol. 131; no. 6; p. jcs212092
• Main Authors: Takagi, Masatoshi, Ono, Takao, Natsume, Toyoaki, Sakamoto, Chiyomi, Nakao, Mitsuyoshi, Saitoh, Noriko, Kanemaki, Masato T, Hirano, Tatsuya, Imamoto, Naoko
• Format: Journal Article
• Language: English
• Published: England The Company of Biologists Ltd 22.03.2018
• Subjects: Cell lines; Chromosomes; Condensin; Depletion; Localization; Phenotypes; Structural integrity; Ki-67; AID; Auxin-inducible degron; Condensin; Mitotic chromosome
• ISSN: 0021-9533; 1477-9137
• DOI: 10.1242/jcs.212092

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.