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Title: Insights into Mad2 Regulation in the Spindle Checkpoint Revealed by the Crystal Structure of the Symmetric Mad2 Dimer

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/CCdc20 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.

Authors:
; ; ; ; ; ; ;  [1]
  1. UTSMC
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
USDOE
OSTI Identifier:
1006707
Resource Type:
Journal Article
Journal Name:
PLoS Biol.
Additional Journal Information:
Journal Volume: 6; Journal Issue: (3) ; 03, 2008; Journal ID: ISSN 1544-9173
Country of Publication:
United States
Language:
ENGLISH
Subject:
60 APPLIED LIFE SCIENCES; CHROMATIDS; CONVERSION; CRYSTAL STRUCTURE; DIMERS; FUNCTIONALS; IN VITRO; INHIBITION; MITOSIS; MUTANTS; PROTEINS; REGULATIONS

Citation Formats

Yang, Maojun, Li, Bing, Liu, Chyong-Jy, Tomchick, Diana R, Machius, Mischa, Rizo, Josep, Yu, Hongtao, and Luo, Xuelian. Insights into Mad2 Regulation in the Spindle Checkpoint Revealed by the Crystal Structure of the Symmetric Mad2 Dimer. United States: N. p., 2008. Web. doi:10.1371/journal.pbio.0060050.
Yang, Maojun, Li, Bing, Liu, Chyong-Jy, Tomchick, Diana R, Machius, Mischa, Rizo, Josep, Yu, Hongtao, & Luo, Xuelian. Insights into Mad2 Regulation in the Spindle Checkpoint Revealed by the Crystal Structure of the Symmetric Mad2 Dimer. United States. https://doi.org/10.1371/journal.pbio.0060050
Yang, Maojun, Li, Bing, Liu, Chyong-Jy, Tomchick, Diana R, Machius, Mischa, Rizo, Josep, Yu, Hongtao, and Luo, Xuelian. 2008. "Insights into Mad2 Regulation in the Spindle Checkpoint Revealed by the Crystal Structure of the Symmetric Mad2 Dimer". United States. https://doi.org/10.1371/journal.pbio.0060050.
@article{osti_1006707,
title = {Insights into Mad2 Regulation in the Spindle Checkpoint Revealed by the Crystal Structure of the Symmetric Mad2 Dimer},
author = {Yang, Maojun and Li, Bing and Liu, Chyong-Jy and Tomchick, Diana R and Machius, Mischa and Rizo, Josep and Yu, Hongtao and Luo, Xuelian},
abstractNote = {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/CCdc20 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.},
doi = {10.1371/journal.pbio.0060050},
url = {https://www.osti.gov/biblio/1006707}, journal = {PLoS Biol.},
issn = {1544-9173},
number = (3) ; 03, 2008,
volume = 6,
place = {United States},
year = {Wed Aug 20 00:00:00 EDT 2008},
month = {Wed Aug 20 00:00:00 EDT 2008}
}