Our research is aimed at understanding the mechanism of the spindle checkpoint signaling using the combination of structural and biochemical approaches. The spindle checkpoint is a cell-cycle surveillance system that prevents premature sister-chromatid separation in mitosis and ensures the accuracy of chromosome inheritance. A multisubunit ubiquitin ligase complex called the anaphase-promoting complex or cyclosome (APC/C) is required for sister-chromatid separation. The spindle checkpoint protein Mad2 binds to Cdc20, the mitotic activator of APC/C, and inhibits APC/CCdc20, thus delaying the onset of anaphase. Mad2 is positively regulated by Mad1 and inhibited by p31comet. In mitosis, the Mad1-Mad2 core complex recruits cytosolic Mad2 to kinetochores through Mad2 conformational dimerization and converts Mad2 to an intermediate conformer (I-Mad2) more amenable to Cdc20 binding, thus facilitating checkpoint activation. During checkpoint inactivation, p31comet binds to Mad1- or Cdc20-bound Mad2, thereby preventing Mad2 activation and promoting Cdc20 autoubiquitination and the dissociation of Mad2 from Cdc20. We have previously determined the structures of both latent and active conformers of human Mad2 using nuclear magnetic resonance (NMR) spectroscopy. Lately, we have also determined the crystal structures of the symmetric Mad2 dimer and the Mad2-p31comet complex. These structures have provided key insights into Mad2 regulation. In the future research, we will further investigate the regulation of Mad2 by Mad1 and p31comet and study the interaction between Mad2 and Cdc20. First, we will structurally characterize the intermediate Mad2 (I-Mad2) by NMR. Second, we will study the structure and function of the C-terminal domain (CTD) of Mad1. Finally, we will perform both structural and biochemical analysis of the p31comet-Mad2-Cdc20 complexes. Defects of the spindle checkpoint cause aneuploidy (abnormal numbers of chromosomes), which is a prevalent form of genomic instability in human cancers. Our research will shed light on the molecular mechanism of the spindle checkpoint and help us understand the root causes of aneuploidy.
RESEARCH INTERESTS
Structural biology
Nuclear Magnetic Resonance (NMR) spectroscopy
Signal transduction
Cell cycle checkpoints and cancer
RECENT PUBLICATIONS
Yang, M., Li, B., Tomchick, DR., Machius, M., Rizo, J., Yu, H. & Luo, X., "Blockage of Mad2 Activation by p31comet through Structural Mimicry." Cell, 131:744-755, 2007
Yang, M., Li, B., Liu, C., Tomchick, D.R., Machius, M., Rizo, J., Yu, H. & Luo, X., "Insights into Mad2 Regulation in the Spindle Checkpoint Revealed by the Crystal Structure of the Symmetric Mad2 dimer." PLoS Biol., 6:643-655, 2008
SIGNIFICANT PUBLICATIONS
Luo, X., Sanford, D. G., Bullock, P. A. and Bachovchin, W. W., "Solution structure of the origin DNA-binding domain of SV40 T-antigen." Nat. Struct. Biol., 3:1034-1039, 1996
Luo, X., Fang, G., Coldiron, M., Lin, Y., Yu, H., Kirschner, M. W. and Wagner, G., "Structure of the Mad2 spindle assembly checkpoint protein and its interaction with Cdc20." Nat. Struct. Biol., 7:224-229, 2000
Luo, X., Tang, Z., Rizo, J., and Yu, H., "The Mad2 spindle checkpoint protein undergoes similar major conformational changes upon binding to either Mad1 or Cdc20." Mol. Cell, 9:59-71, 2002
Luo, X., Tang, Z., Xia, G., Wassmann, K., Matsumoto, T., Rizo, J., and Yu, H., "The Mad2 Spindle Checkpoint Protein Has Two Distinct Natively Folded States." Nat. Struct. Mol. Biol., 4:338-45, 2004
Yang, M., Li, B., Tomchick, DR., Machius, M., Rizo, J., Yu, H. & Luo, X., "Blockage of Mad2 Activation by p31comet through Structural Mimicry." Cell, 131:744-755, 2007
Point and right click (click and hold for Mac users) your mouse onand select "Save this link (or target) as..." option to save the file to your local computer.
and select "Save this link (or target) as..." option to save the file to your local computer.