The genetic stability of an organism depends on the accurate partition of sister chromatids into two daughter cells during mitosis, which in turn requires the maintenance of the physical linkage (cohesion) between sister chromatids until their bipolar attachment to the mitotic spindle. Removal of cohesin (the protein complex that maintains sister chromatid cohesion) from chromosomes then leads to sister chromatid separation. In vertebrate cells, removal of cohesin occurs in two steps. At prophase, most of cohesin along the chromosome arms is removed through Polo-like kinase (Plk1)/Aurora B-dependent phosphorylation of cohesin. At metaphase, the residual centromeric pool of cohesin is cleaved by separase to allow sister chromatid separation. The long-term goal of my lab is to understand the molecular mechanism of chromosome segregation in mammalian cells. In this proposal, we will address an interesting puzzle in this area: how is the centromeric cohesin shielded from the actions of Plk1 /Aurora B in prophase? We have recently provided evidence to suggest that the spindle checkpoint kinase Bub1 targets and the Sgo1 centromeric protein and protein phosphatase 2A (PP2A) to centromeres where they counteract the phosphorylation of cohesin by Plk1 and other mitotic kinases.
In Specific Aims 1 and 2, we will further delineate the mechanisms by which Bub1, Sgo1, and PP2A collaborate to protect centromeric cohesion. On the other hand, our results also point to a PP2A-independent role of Sgo1. Indeed, we have made two novel and related findings in the past year. Sgo1 directly interacts with an RNA-binding protein complex called ILF2-ILF3 (interleukin enhancer binding factors 2 and 3). Sgo1 itself binds to RNA in vitro. Experiments are planned in Aims 3 and 4 to establish the in vivo relevance of these findings. Premature loss of centromeric sister chromatid cohesion leads to chromosome missegregation and abnormal numbers of chromosomes in daughter cells (aneuploidy), which contributes to cancer formation and birth defects. The proposed research will shed light on the mechanism of chromosome segregation and may in turn lead to better understanding and prevention of chromosomal instability and aneuploidy in human cancers and birth defects, such as Down Syndrome.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM076481-04
Application #
7884116
Study Section
Nuclear Dynamics and Transport (NDT)
Program Officer
Zatz, Marion M
Project Start
2007-08-10
Project End
2012-05-31
Budget Start
2010-06-01
Budget End
2012-05-31
Support Year
4
Fiscal Year
2010
Total Cost
$309,210
Indirect Cost
Name
University of Texas Sw Medical Center Dallas
Department
Pharmacology
Type
Schools of Medicine
DUNS #
800771545
City
Dallas
State
TX
Country
United States
Zip Code
75390
Liu, Hong; Rankin, Susannah; Yu, Hongtao (2013) Phosphorylation-enabled binding of SGO1-PP2A to cohesin protects sororin and centromeric cohesion during mitosis. Nat Cell Biol 15:40-9
Ke, Yuwen; Huh, Jae-Wan; Warrington, Ross et al. (2011) PICH and BLM limit histone association with anaphase centromeric DNA threads and promote their resolution. EMBO J 30:3309-21
Yu, Hongtao (2011) A mad partner for Shugoshin in meiosis. EMBO J 30:2759-61
Kim, Soonjoung; Yu, Hongtao (2011) Mutual regulation between the spindle checkpoint and APC/C. Semin Cell Dev Biol 22:551-8
Kang, Jungseog; Chaudhary, Jaideep; Dong, Hui et al. (2011) Mitotic centromeric targeting of HP1 and its binding to Sgo1 are dispensable for sister-chromatid cohesion in human cells. Mol Biol Cell 22:1181-90
Hou, Haifeng; Yu, Hongtao (2010) Structural insights into histone lysine demethylation. Curr Opin Struct Biol 20:739-48
Karamysheva, Zemfira; Diaz-Martinez, Laura A; Crow, Sara E et al. (2009) Multiple anaphase-promoting complex/cyclosome degrons mediate the degradation of human Sgo1. J Biol Chem 284:1772-80
Kang, Jungseog; Yang, Maojun; Li, Bing et al. (2008) Structure and substrate recruitment of the human spindle checkpoint kinase Bub1. Mol Cell 32:394-405