p53 and p21(Waf1) are recruited to distinct PML-containing nuclear foci in irradiated and Nutlin-3a-treated U2OS cells.
Promyelocytic leukemia nuclear bodies (PML-NBs) are multiprotein complexes that include PML protein and localize in nuclear foci. PML-NBs are implicated in multiple stress responses, including apoptosis, DNA repair, and p53-dependent growth inhibition. ALT-associated PML bodies (APBs) are specialized PML-NBs that include telomere-repeat binding-factor TRF1 and are exclusively in telomerase-negative tumors where telomere length is maintained through alternative (ALT) recombination mechanisms. We compared cell-cycle and p53 responses in ALT-positive cancer cells (U2OS) exposed to ionizing radiation (IR) or the p53 stabilizer Nutlin-3a. Both IR and Nutlin-3a caused growth arrest and comparable induction of p53. However, p21, whose gene p53 activates, displayed biphasic induction following IR and monophasic induction following Nutlin-3a. p53 was recruited to PML-NBs 3-4 days after IR, approximately coincident with the secondary p21 increase. These p53/PML-NBs marked sites of apparently unrepaired DNA double-strand breaks (DSBs), identified by colocalization with phosphorylated histone H2AX. Both Nutlin-3a and IR caused a large increase in APBs that was dependent on p53 and p21 expression. Moreover, p21, and to a lesser extent p53, was recruited to APBs in a fraction of Nutlin-3a-treated cells. These data indicate (1) p53 is recruited to PML-NBs after IR that likely mark unrepaired DSBs, suggesting p53 may either be further activated at these sites and/or function in their repair; (2) p53-p21 pathway activation increases the percentage of APB-positive cells, (3) p21 and p53 are recruited to ALT-associated PML-NBs after Nutlin-3a treatment, suggesting that they may play a previously unrecognized role in telomere maintenance.
Shen
Hong
H
Department of Anatomy and Cell Biology, Rush University Medical Center, 1750 W Harrison Ave., Jelke Building, Room 1306, Chicago, Illinois, USA.
Maki
Carl G
CG
D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000737:chemistry / Q000648:ultrastructure; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D004260:DNA Repair; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D046912:Multiprotein Complexes; D009687:Nuclear Proteins / Q000378:metabolism*; D012516:Osteosarcoma / Q000473:pathology*; D010879:Piperazines / Q000494:pharmacology*; D000071156:Promyelocytic Leukemia Protein; D021381:Protein Transport; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors; D016615:Telomere; D014157:Transcription Factors / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D007093:Imidazoles; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D010879:Piperazines; D000071156:Promyelocytic Leukemia Protein; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C070576:PML protein, human; C482205:nutlin 3; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2
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