Septin 7 interacts with centromere-associated protein E and is required for its kinetochore localization

J Biol Chem. 2008 Jul 4;283(27):18916-25. doi: 10.1074/jbc.M710591200. Epub 2008 May 6.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium-Binding Proteins / genetics
  • Calcium-Binding Proteins / metabolism
  • Cell Cycle Proteins / antagonists & inhibitors
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Chromosomal Proteins, Non-Histone / genetics
  • Chromosomal Proteins, Non-Histone / metabolism*
  • Chromosome Segregation / physiology*
  • Chromosomes, Human / genetics
  • Chromosomes, Human / metabolism*
  • Dogs
  • HeLa Cells
  • Humans
  • Kinetochores / metabolism*
  • Mad2 Proteins
  • Metaphase / physiology
  • Phosphoric Monoester Hydrolases / genetics
  • Phosphoric Monoester Hydrolases / metabolism
  • Protein Binding / physiology
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism
  • Protein Structure, Tertiary / physiology
  • RNA, Small Interfering / genetics
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism
  • Septins
  • Spindle Apparatus / genetics
  • Spindle Apparatus / metabolism*

Substances

  • Calcium-Binding Proteins
  • Cell Cycle Proteins
  • Chromosomal Proteins, Non-Histone
  • MAD2L1 protein, human
  • Mad2 Proteins
  • RNA, Small Interfering
  • Repressor Proteins
  • centromere protein E
  • BUB1 protein, human
  • Bub1 spindle checkpoint protein
  • Protein Serine-Threonine Kinases
  • Phosphoric Monoester Hydrolases
  • SEPTIN7 protein, human
  • Septins