title: Association of the circadian factor Period 2 to p53 influences p53's function in DNA-damage signaling.
abstract: Circadian period proteins influence cell division and death by associating with checkpoint components, although their mode of regulation has not been firmly established. hPer2 forms a trimeric complex with hp53 and its negative regulator Mdm2. In unstressed cells, this association leads to increased hp53 stability by blocking Mdm2-dependent ubiquitination and transcription of hp53 target genes. Because of the relevance of hp53 in checkpoint signaling, we hypothesize that hPer2 association with hp53 acts as a regulatory module that influences hp53's downstream response to genotoxic stress. Unlike the trimeric complex, whose distribution was confined to the nuclear compartment, hPer2/hp53 was identified in both cytosol and nucleus. At the transcriptional level, a reporter containing the hp21(WAF1/CIP1) promoter, a target of hp53, remained inactive in cells expressing a stable form of the hPer2/hp53 complex even when treated with γ-radiation. Finally, we established that hPer2 directly acts on the hp53 node, as checkpoint components upstream of hp53 remained active in response to DNA damage. Quantitative transcriptional analyses of hp53 target genes demonstrated that unbound hp53 was absolutely required for activation of the DNA-damage response. Our results provide evidence of the mode by which the circadian tumor suppressor hPer2 modulates hp53 signaling in response to genotoxic stress.
authors.affiliation: Integrated Cellular Responses Laboratory, Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Gotoh
authors.affiliation: Integrated Cellular Responses Laboratory, Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
authors.forename: Marian
authors.initials: M
authors.lastname: Vila-Caballer
authors.affiliation: Integrated Cellular Responses Laboratory, Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Liu
authors.affiliation: Integrated Cellular Responses Laboratory, Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
authors.forename: Samuel
authors.initials: S
authors.lastname: Schiffhauer
authors.affiliation: Integrated Cellular Responses Laboratory, Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 finkielc@vt.edu.
authors.forename: Carla V
authors.initials: CV
authors.lastname: Finkielstein
mesh_terms: D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004249:DNA Damage; D015972:Gene Expression Regulation, Neoplastic; D045325:HCT116 Cells; D006801:Humans; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D056950:Period Circadian Proteins / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C421902:PER2 protein, human; D056950:Period Circadian Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53