title: CHK1 cleavage in programmed cell death is intricately regulated by both caspase and non-caspase family proteases.
abstract: BACKGROUND
  CHK1 is an important effector kinase that regulates the cell cycle checkpoint. Previously, we showed that CHK1 is cleaved in a caspase (CASP)-dependent manner during DNA damage-induced programmed cell death (PCD) and have examined its physiological roles.
  
  
  RESULTS
  In this study, we investigated the behavior of CHK1 in PCD. Firstly, we found that CHK1 is cleaved at three sites in PCD, and all cleavages were inhibited by the co-treatment of a pan-CASP inhibitor or serine protease inhibitors. We also showed that CHK1 is cleaved by CASP3 and/or CASP7 recognizing at (296)SNLD(299) and (348)TCPD(351), and that the cleavage results in the enhancement of CHK1 kinase activity. Furthermore, as a result of the characterization of cleavage sites by site-directed mutagenesis and an analysis performed using deletion mutants, we identified (320)EPRT(323) as an additional cleavage recognition sequence. Considering the consensus sequence cleaved by CASP, it is likely that CHK1 is cleaved by non-CASP family protease(s) recognizing at (320)EPRT(323). Additionally, the cleavage catalyzed by the (320)EPRT(323) protease(s) markedly and specifically increased when U2OS cells synchronized into G1 phase were induced to PCD by cisplatin treatment.
  
  
  CONCLUSIONS
  CHK1 cleavage is directly and indirectly regulated by CASP and non-CASP family proteases including serine protease(s) and the "(320)EPRT(323) protease(s)." Furthermore, (320)EPRT(323) cleavage of CHK1 occurs efficiently in PCD which is induced at the G1 phase by DNA damage.
  
  
  CONCLUSIONS
  CASP and non-CASP family proteases intricately regulate cleavage for up-regulation of CHK1 kinase activity during PCD.
authors.affiliation: Department of Molecular Pathology and Metabolic Disease, Tokyo University of Science, Chiba, Japan. nokita7@rs.noda.tus.ac.jp
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Okita
authors.forename: Miyuki
authors.initials: M
authors.lastname: Yoshimura
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Watanabe
authors.forename: Shota
authors.initials: S
authors.lastname: Minato
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kudo
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Higami
authors.forename: Sei-ichi
authors.initials: S
authors.lastname: Tanuma
mesh_terms: D020816:Amino Acid Motifs; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism*; D053179:Caspase 7 / Q000235:genetics / Q000378:metabolism*; D059447:Cell Cycle Checkpoints / Q000187:drug effects / Q000502:physiology; D000071877:Checkpoint Kinase 1; D002945:Cisplatin / Q000494:pharmacology; D004249:DNA Damage / Q000502:physiology; D016193:G1 Phase / Q000187:drug effects / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D059748:Proteolysis; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D015842:Serine Proteinase Inhibitors; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C505407:CASP3 protein, human; C505520:CASP7 protein, human; D053148:Caspase 3; D053179:Caspase 7; D002945:Cisplatin