title: Chk2 mediates stabilization of the FoxM1 transcription factor to stimulate expression of DNA repair genes.
abstract: The forkhead box M1 (FoxM1) transcription factor regulates expression of cell cycle genes essential for DNA replication and mitosis during organ repair and cancer progression. Here, we demonstrate that FoxM1-deficient (-/-) mouse embryonic fibroblasts and osteosarcoma U2OS cells depleted in FoxM1 levels by small interfering RNA transfection display increased DNA breaks, as evidenced by immunofluorescence focus staining for phosphospecific histone H2AX. FoxM1-deficient cells also exhibit stimulation of p53 transcriptional activity, as evidenced by increased expression of the p21(cip1) gene. FoxM1-deficient cells display reduced expression of the base excision repair factor X-ray cross-complementing group 1 (XRCC1) and breast cancer-associated gene 2 (BRCA2), the latter of which is involved in homologous recombination repair of DNA double-strand breaks. Furthermore, FoxM1 protein is phosphorylated by checkpoint kinase 2 (Chk2) in response to DNA damage. This phosphorylation of FoxM1 on serine residue 361 caused increased stability of the FoxM1 protein with corresponding increased transcription of XRCC1 and BRCA2 genes, both of which are required for repair of DNA damage. These results identify a novel role for FoxM1 in the transcriptional response during DNA damage/checkpoint signaling and show a novel mechanism by which Chk2 protein regulates expression of DNA repair enzymes.
authors.affiliation: Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607, USA. ytan1231@yahoo.com.
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Tan
authors.forename: Pradip
authors.initials: P
authors.lastname: Raychaudhuri
authors.forename: Robert H
authors.initials: RH
authors.lastname: Costa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D024682:BRCA2 Protein / Q000235:genetics / Q000378:metabolism*; D064447:Checkpoint Kinase 2; D053960:DNA Breaks; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005047:Etoposide / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000528:radiation effects; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000235:genetics*; D006801:Humans; D007259:Infrared Rays; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects; D013816:Thermodynamics; D014158:Transcription, Genetic / Q000187:drug effects / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014466:Ultraviolet Rays; D000076105:X-ray Repair Cross Complementing Protein 1
chemical_list: D024682:BRCA2 Protein; D004268:DNA-Binding Proteins; C107585:FOXM1 protein, human; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors; C491524:Foxm1 protein, mouse; D016159:Tumor Suppressor Protein p53; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human; C000619352:Xrcc1 protein, mouse; D012694:Serine; D005047:Etoposide; D064447:Checkpoint Kinase 2; C578634:CHEK2 protein, human; C578633:Chek2 protein, mouse; D017346:Protein Serine-Threonine Kinases