title: Chk2 splice variants express a dominant-negative effect on the wild-type Chk2 kinase activity.
abstract: While the majority of RNA transcripts from protein-encoding genes in the human genome are subject to physiological splicing, pathological splicing is increasingly reported in cancer tissue. Previously, we identified >90 different splice variants of Chk2, a gene encoding a serine/threonine kinase propagating the DNA damage signal by phosphorylating and activating several downstream substrates like p53, Cdc25A, and Cdc25C involved in cell cycle arrest and apoptosis. While alternative splice forms of other genes have been reported to exert a dominant-negative effect on the wild-type molecules, the function of Chk2 splice protein variants is still unclear. Here we evaluated the function of four Chk2 splice proteins for which mRNA splice variants were identified in human breast carcinomas. These splice variants were stably expressed as nuclear proteins. Two splice forms (Chk2Delta4 and Chk2del(2-3)) expressed kinase activity while variants Chk2Delta11 and Chk2isoI were essentially kinase inactive. Independent of intrinsic kinase activity, each splice variant impaired wild-type Chk2 activity through heterodimerization. Based on our findings, we suggest alternative splicing as a possible novel mechanism for repression of the Chk2 wild-type function.
authors.affiliation: Department of Molecular Biology, University of Bergen, N-5020 Bergen, Norway; Section of Oncology, Institute of Medicine, University of Bergen, N-5021 Bergen, Norway.
authors.forename: Elisabet Ognedal
authors.initials: EO
authors.lastname: Berge
authors.forename: Vidar
authors.initials: V
authors.lastname: Staalesen
authors.forename: Anne Hege
authors.initials: AH
authors.lastname: Straume
authors.forename: Johan Richard
authors.initials: JR
authors.lastname: Lillehaug
authors.forename: Per Eystein
authors.initials: PE
authors.lastname: Lønning
mesh_terms: D017398:Alternative Splicing; D064007:Ataxia Telangiectasia Mutated Proteins; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D064447:Checkpoint Kinase 2; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D055503:Protein Multimerization; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D013379:Substrate Specificity; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D020033:Protein Isoforms; D025521:Tumor Suppressor Proteins; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases