title: Chk1 is required for the metaphase-anaphase transition via regulating the expression and localization of Cdc20 and Mad2.
abstract: OBJECTIVE
  The checkpoint kinase 1 (Chk1) functions not only in genotoxic stresses but also in normal cell cycle progression, particularly in the initiation, progression and fidelity of unperturbed mitosis. In this study, we investigated the role of Chk1 in regulating the metaphase-anaphase transition in mammalian cells.
  
  
  METHODS
  The mitotic progression was monitored by flow cytometry analysis. The levels of cyclin B1, Cdc20 and Mad2 were measured by Western blotting. Metaphase chromosome alignment and the subcellular localization of Cdc20 and Mad2 were analyzed by immunofluorescence and confocal microscopy.
  
  
  RESULTS
  Cyclin B1 degradation and the metaphase-anaphase transition were severely blocked by Chk1 siRNA. Depletion of Chk1 induced chromosome alignment defect in metaphase cells. The kinetochore localization of Cdc20, Mad2 was disrupted in Chk1 depleted cells. Chk1 abrogation also dramatically reduced the protein expression levels of Cdc20 and Mad2.
  
  
  CONCLUSIONS
  These results strongly suggest that Chk1 is required for the metaphase-anaphase transition via regulating the subcellular localization and the expression of Cdc20 and Mad2.
authors.affiliation: School of Life Sciences, Tsinghua University, Beijing 100084, PR China; Key Lab in Healthy Science and Technology, Division of Life Science, Graduate School at Shenzhen, Tsinghua University, Shenzhen, Guangdong Province, PR China.
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Yang
authors.affiliation: School of Life Sciences, Tsinghua University, Beijing 100084, PR China; Key Lab in Healthy Science and Technology, Division of Life Science, Graduate School at Shenzhen, Tsinghua University, Shenzhen, Guangdong Province, PR China.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.affiliation: Department of Clinical Oncology, Wuhan No. 1 Hospital, Wuhan, Hubei Province, PR China.
authors.forename: Zuowei
authors.initials: Z
authors.lastname: Hu
authors.affiliation: Key Lab in Healthy Science and Technology, Division of Life Science, Graduate School at Shenzhen, Tsinghua University, Shenzhen, Guangdong Province, PR China.
authors.forename: Yaou
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Lab in Healthy Science and Technology, Division of Life Science, Graduate School at Shenzhen, Tsinghua University, Shenzhen, Guangdong Province, PR China. Electronic address: xu.naihan@sz.tsinghua.edu.cn.
authors.forename: Naihan
authors.initials: N
authors.lastname: Xu
mesh_terms: D000705:Anaphase / Q000502:physiology*; D064199:Cdc20 Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D000071877:Checkpoint Kinase 1; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000737:chemistry / Q000378:metabolism; D064246:Mad2 Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D008677:Metaphase / Q000502:physiology*; D011494:Protein Kinases / Q000502:physiology*
chemical_list: D064199:Cdc20 Proteins; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; C577488:CDC20 protein, human; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1
keywords: Cdc20; Chk1; Mad2; Metaphase–anaphase transition; Spindle checkpoint