title: Septin 7 interacts with centromere-associated protein E and is required for its kinetochore localization.
abstract: Chromosome segregation in mitosis is orchestrated by dynamic interaction between spindle microtubules and the kinetochore. Septin (SEPT) belongs to a conserved family of polymerizing GTPases localized to the metaphase spindle during mitosis. Previous study showed that SEPT2 depletion results in chromosome mis-segregation correlated with a loss of centromere-associated protein E (CENP-E) from the kinetochores of congressing chromosomes (1). However, it has remained elusive as to whether CENP-E physically interacts with SEPT and how this interaction orchestrates chromosome segregation in mitosis. Here we show that SEPT7 is required for a stable kinetochore localization of CENP-E in HeLa and MDCK cells. SEPT7 stabilizes the kinetochore association of CENP-E by directly interacting with its C-terminal domain. The region of SEPT7 binding to CENP-E was mapped to its C-terminal domain by glutathione S-transferase pull-down and yeast two-hybrid assays. Immunofluorescence study shows that SEPT7 filaments distribute along the mitotic spindle and terminate at the kinetochore marked by CENP-E. Remarkably, suppression of synthesis of SEPT7 by small interfering RNA abrogated the localization of CENP-E to the kinetochore and caused aberrant chromosome segregation. These mitotic defects and kinetochore localization of CENP-E can be successfully rescued by introducing exogenous GFP-SEPT7 into the SEPT7-depleted cells. These SEPT7-suppressed cells display reduced tension at kinetochores of bi-orientated chromosomes and activated mitotic spindle checkpoint marked by Mad2 and BubR1 labelings on these misaligned chromosomes. These findings reveal a key role for the SEPT7-CENP-E interaction in the distribution of CENP-E to the kinetochore and achieving chromosome alignment. We propose that SEPT7 forms a link between kinetochore distribution of CENP-E and the mitotic spindle checkpoint.
authors.affiliation: Division of Cellular Dynamics, Hefei National Laboratory for Physical Sciences at Microscale and the University of Science and Technology of China, Hefei 230027, China.
authors.forename: Mei
authors.initials: M
authors.lastname: Zhu
authors.forename: Fengsong
authors.initials: F
authors.lastname: Wang
authors.forename: Feng
authors.initials: F
authors.lastname: Yan
authors.forename: Phil Y
authors.initials: PY
authors.lastname: Yao
authors.forename: Jian
authors.initials: J
authors.lastname: Du
authors.forename: Xinjiao
authors.initials: X
authors.lastname: Gao
authors.forename: Xiwei
authors.initials: X
authors.lastname: Wang
authors.forename: Quan
authors.initials: Q
authors.lastname: Wu
authors.forename: Tarsha
authors.initials: T
authors.lastname: Ward
authors.forename: Jingjing
authors.initials: J
authors.lastname: Li
authors.forename: Steve
authors.initials: S
authors.lastname: Kioko
authors.forename: Renming
authors.initials: R
authors.lastname: Hu
authors.forename: Wei
authors.initials: W
authors.lastname: Xie
authors.forename: Xia
authors.initials: X
authors.lastname: Ding
authors.forename: Xuebiao
authors.initials: X
authors.lastname: Yao
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D020090:Chromosome Segregation / Q000502:physiology*; D002877:Chromosomes, Human / Q000235:genetics / Q000378:metabolism*; D004285:Dogs; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D064246:Mad2 Proteins; D008677:Metaphase / Q000502:physiology; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D034741:RNA, Small Interfering / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D058112:Septins; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism*
chemical_list: D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D034741:RNA, Small Interfering; D012097:Repressor Proteins; C068688:centromere protein E; C584277:BUB1 protein, human; C090464:Bub1 spindle checkpoint protein; D017346:Protein Serine-Threonine Kinases; D010744:Phosphoric Monoester Hydrolases; C113158:SEPTIN7 protein, human; D058112:Septins