The human homologs of checkpoint kinases Chk1 and Cds1 (Chk2) phosphorylate p53 at multiple DNA damage-inducible sites.

By S. Shieh, Jinwoo Ahn, K. Tamai, Y. Taya, Carol Prives. Genes & Development, 2000

1,079 citations recorded by the source corpus.

Upon DNA damage, the amino terminus of p53 is phosphorylated at a number of serine residues including S20, a site that is particularly important in regulating stability and function of the protein. Because no known kinase has been identified that can modify this site, HeLa nuclear extracts were fractionated and S20 phosphorylation was followed. We discovered that a S20 kinase activity copurifies with the human homolog of the Schizosaccharomyces pombe checkpoint kinase, Chk1 (hCHK1). We confirmed that recombinant hCHK1, but not a kinase-defective version of hCHK1, can phosphorylate p53 in vitro at S20. Additional inducible amino- and carboxy-terminal sites in p53 are also phosphorylated by hCHK1, indicating that this is an unusually versatile protein kinase. It is interesting that hCHK1 strongly prefers tetrameric to monomeric p53 in vitro, consistent with our observation that phosphorylation of amino-terminal sites in vivo requires that p53 be oligomeric. Regulation of the levels and activity of hCHK1 in transfected cells is directly correlated with the levels of p53; expression of either a kinase-defective hCHK1 or antisense hCHK1 leads to reduced levels of cotransfected p53, whereas overexpression of wild-type hCHK1 or the kinase domain of hCHK1 results in increased levels of expressed p53 protein. The human homolog of the second S. pombe checkpoint kinase, Cds1 (CHK2/hCds1), phosphorylates tetrameric p53 but not monomeric p53 in vitro at sites similar to those phosphorylated by hCHK1 kinase, suggesting that both checkpoint kinases can play roles in regulating p53 after DNA damage.

Subfields: Cell Biology, Molecular Biology, Oncology

View Paper: https://www.semanticscholar.org/paper/909c1709fd8dd56c2f9f82cd8db0715ff33a265a

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Citations in the corpus

• p53-deficient cells rely on ATM- and ATR-mediated checkpoint signaling through the p38MAPK/MK2 pathway for survival after DNA damage. (2007, background): “Although not shown explicitly in the diagram, Chk1 also directly phosphorylates p53 (Shieh et al., 2000).”
• USP10 Regulates p53 Localization and Stability by Deubiquitinating p53 (2010, neutral): “For example, p53 is phosphorylated at Ser20 by the checkpoint kinase Chk2 after IR, which results in p53’s dissociation from Mdm2 and its subsequent stabilization (Chehab et al., 2000; Hirao et al., 2000; Shieh et al., 2000).”
• DNA damage-induced cell death: from specific DNA lesions to the DNA damage response and apoptosis. (2013, background): “In turn, Chk2 and Chk1 phosphorylate the transcription factor p53 at Ser20 [116].”
• Cell cycle checkpoint signaling through the ATM and ATR kinases. (2001, background): “ATM activates hChk2 by phosphorylating an amino terminal Thr residue (Thr 68) (Ahn et al. 2000; Melchionna et al. 2000), and hChk2, in turn, phosphorylates yet another amino-terminal Ser residue (Ser 20) in p53 (Chehab et al. 2000; Hirao et al. 2000; Shieh et al. 2000).”
• Toward maintaining the genome: DNA damage and replication checkpoints. (2002, background): “This phosphorylation by ATM likely causes p53 transcriptional activation (51), while phosphorylation of p53 at Ser 20 by Chk2 acting downstream of ATM, reduces the ability of ubiquitin ligase Mdm2 to bind p53, thus promoting its stabilization (34, 87, 90, 169).”
• Mechanisms of human DNA repair: an update. (2003, background): “Both Chk2 and Chk1 are able to phosphorylate p53 at Ser20 (Shieh et al., 2000), giving rise to blockage of the MDM2-binding site-thus leading to release of p53 from MDM2-a protein that normally targets p53 for ubiquitin-dependent degradation (Chehab et al., 1999, 2000; Hirao et al., 2000; Unger et a”