Cell cycle differences in DNA damage-induced BRCA1 phosphorylation affect its subcellular localization.
Phosphorylation of BRCA1 tumor suppressor protein is regulated during the cell cycle and in response to DNA damage. Several Ser/Thr kinases have been implicated in BRCA1 phosphorylation, including ATM/ATR, cdk2, and hChk2 kinases. In this study, phospho-Ser-specific antibodies recognizing Ser-988, -1423, -1497, and -1524 residues of BRCA1 were employed to study BRCA1 phosphorylation during the S and G2/M phases under conditions of DNA damage. We observed that IR (ionizing radiation) treatment induced phosphorylation of Ser-988/Ser-1524 during the S phase and of Ser-988/Ser-1423 during the G2/M phase. UV treatment induced phosphorylation of Ser-988 during the S phase and of Ser-1423 during the G2/M phase. Phosphorylation of serines 1423 and -1524 was not induced in HCC1937 breast cancer cells, which contain mutant BRCA1 protein. Confocal microscopy revealed that unphosphorylated BRCA1 localizes on chromosomes from metaphase through telophase, whereas Ser-988-phosphorylated BRCA1 resides in the inner chromosomal structure, centrosome, and the cleavage furrow during prophase through telophase. We also found that Ser-988-phosphorylated BRCA1 relocalizes to the perinuclear region when cells are subjected to IR or UV radiation in the S phase. These results reinforce a model wherein phosphorylation of specific residues of BRCA1 after DNA damage affects its localization and function.
Okada
Shinya
S
Derald H. Ruttenberg Cancer Center, The Mount Sinai School of Medicine, New York University, New York, New York 10029, USA.
Ouchi
Toru
T
D000595:Amino Acid Sequence; D019313:BRCA1 Protein / Q000378:metabolism*; D002453:Cell Cycle; D004249:DNA Damage; D005434:Flow Cytometry; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D014407:Tumor Cells, Cultured
D019313:BRCA1 Protein