title: CHK2 stability is regulated by the E3 ubiquitin ligase SIAH2.
abstract: The serine threonine checkpoint kinase 2 (CHK2) is a critical protein involved in the DNA damage-response pathway, which is activated by phosphorylation inducing cellular response such as DNA repair, cell-cycle regulation or apoptosis. Although CHK2 activation mechanisms have been amply described, very little is known about degradation control processes. In the present study, we identify the ubiquitin E3 ligase SIAH2 as an interaction partner of CHK2, which mediates its ubiquitination and proteasomal degradation. CHK2 degradation is independent of both its activation and its kinase activity, but also of the phosphorylation in S456. We show that SIAH2-deficient cells present CHK2 accumulation together with lower ubiquitination levels. Accordingly, SIAH2 depletion by siRNA increases CHK2 levels. In response to DNA damage induced by etoposide, interaction between both proteins is disrupted, thus avoiding CHK2 degradation and promoting its stabilization. We also found that CHK2 phosphorylates SIAH2 at three residues (Thr26, Ser28 and Thr119), modifying its ability to regulate certain substrates. Cellular arrest in the G2/M phase induced by DNA damage is reverted by SIAH2 expression through the control of CHK2 levels. We observed that hypoxia decreases CHK2 levels in parallel to SIAH2 induction. Similarly, we provide evidence suggesting that resistance to apoptosis induced by genotoxic agents in cells subjected to hypoxia could be partly explained by the mutual regulation between both proteins. These results indicate that SIAH2 regulates CHK2 basal turnover, with important consequences on cell-cycle control and on the ability of hypoxia to alter the DNA damage-response pathway in cancer cells.
authors.affiliation: Department of Cell Biology, Physiology and Immunology, University of Córdoba, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)/Hospital, Universitario Reina Sofía, Córdoba, Spain.
authors.forename: C
authors.initials: C
authors.lastname: García-Limones
authors.affiliation: Department of Cell Biology, Physiology and Immunology, University of Córdoba, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)/Hospital, Universitario Reina Sofía, Córdoba, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Lara-Chica
authors.affiliation: Department of Cell Biology, Physiology and Immunology, University of Córdoba, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)/Hospital, Universitario Reina Sofía, Córdoba, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Jiménez-Jiménez
authors.affiliation: Department of Cell Biology, Physiology and Immunology, University of Córdoba, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)/Hospital, Universitario Reina Sofía, Córdoba, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Pérez
authors.affiliation: Department of Cell Biology, Physiology and Immunology, University of Córdoba, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)/Hospital, Universitario Reina Sofía, Córdoba, Spain.
authors.forename: P
authors.initials: P
authors.lastname: Moreno
authors.affiliation: Department of Cell Biology, Physiology and Immunology, University of Córdoba, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)/Hospital, Universitario Reina Sofía, Córdoba, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Muñoz
authors.affiliation: Department of Cell Biology, Physiology and Immunology, University of Córdoba, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)/Hospital, Universitario Reina Sofía, Córdoba, Spain.
authors.forename: M A
authors.initials: MA
authors.lastname: Calzado
mesh_terms: D059447:Cell Cycle Checkpoints; D064447:Checkpoint Kinase 2 / Q000032:analysis / Q000378:metabolism*; D004249:DNA Damage; D004795:Enzyme Stability; D057809:HEK293 Cells; D006801:Humans; D009687:Nuclear Proteins / Q000032:analysis / Q000502:physiology*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000502:physiology; D044767:Ubiquitin-Protein Ligases / Q000032:analysis / Q000502:physiology*; D054875:Ubiquitination; D000098563:Seven in Absentia Proteins
chemical_list: D009687:Nuclear Proteins; D044767:Ubiquitin-Protein Ligases; D000098563:Seven in Absentia Proteins; D064447:Checkpoint Kinase 2; C578634:CHEK2 protein, human; D046988:Proteasome Endopeptidase Complex