Insights into Mad2 regulation in the spindle checkpoint revealed by the crystal structure of the symmetric Mad2 dimer

Maojun Yang, Bing Li, Chyong Jy Liu, Diana R Tomchick, Mischa Machius, Jose Rizo-Rey, Hongtao Yu, Xuelian Luo

Research output: Contribution to journalArticle

63 Citations (Scopus)

Abstract

In response to misaligned sister chromatids during mitosis, the spindle checkpoint protein Mad2 inhibits the anaphase-promoting complex or cyclosome (APC/C) through binding to its mitotic activator Cdc20, thus delaying anaphase onset. Mad1, an upstream regulator of Mad2, forms a tight core complex with Mad2 and facilitates Mad2 binding to Cdc20. In the absence of its binding proteins, free Mad2 has two natively folded conformers, termed N1-Mad2/open-Mad2 (O-Mad2) and N2-Mad2/closed Mad2 (C-Mad2), with C-Mad2 being more active in APC/C Cdc20 inhibition. Here, we show that whereas O-Mad2 is monomeric, C-Mad2 forms either symmetric C-Mad2-C-Mad2 (C-C) or asymmetric O-Mad2-C-Mad2 (O-C) dimers. We also report the crystal structure of the symmetric C-C Mad2 dimer, revealing the basis for the ability of unliganded C-Mad2, but not O-Mad2 or liganded C-Mad2, to form symmetric dimers. A Mad2 mutant that predominantly forms the C-C dimer is functional in vitro and in living cells. Finally, the Mad1-Mad2 core complex facilitates the conversion of O-Mad2 to C-Mad2 in vitro. Collectively, our results establish the existence of a symmetric Mad2 dimer and provide insights into Mad1-assisted conformational activation of Mad2 in the spindle checkpoint.

Original languageEnglish (US)
Article numbere50
Pages (from-to)643-655
Number of pages13
JournalPLoS Biology
Volume6
Issue number3
DOIs
StatePublished - Mar 2008

Fingerprint

Anaphase-Promoting Complex-Cyclosome
crystal structure
Dimers
Mad2 Proteins
Crystal structure
Anaphase
Chromatids
chromatids
anaphase
Mitosis
mitosis
binding proteins
Carrier Proteins
mutants
proteins
cells
Chemical activation
Cells
In Vitro Techniques
anaphase promoting complex

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Neuroscience(all)

Cite this

Insights into Mad2 regulation in the spindle checkpoint revealed by the crystal structure of the symmetric Mad2 dimer. / Yang, Maojun; Li, Bing; Liu, Chyong Jy; Tomchick, Diana R; Machius, Mischa; Rizo-Rey, Jose; Yu, Hongtao; Luo, Xuelian.

In: PLoS Biology, Vol. 6, No. 3, e50, 03.2008, p. 643-655.

Research output: Contribution to journalArticle

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