Kinetics of BRCA1 regulation in response to UVC radiation.
To investigate changes in BRCA1 following DNA damage, we exposed MCF-7 cells to increasing doses of ultraviolet C. We observed an increase in BRCA1 protein levels above 78 J/m2. This increase was observed as early as 5 min after irradiation. BRCA1 levels were then observed to decrease after 2 h, consistent with the previously published data. By pretreating with cycloheximide prior to irradiation, we observed a decrease in the protein half-life, from 3.5 h to 53 min, suggesting that a decrease in protein half-life may cause the lower levels of BRCA1 after irradiation. We also observed an increase in BRCA1 mRNA within 15 min of irradiation, followed by a decrease after 4 h. These data suggest that newly translated protein may contribute to increases in BRCA1 protein levels. The very rapid changes in BRCA1 support its role as a sensor of DNA damage, as opposed to being a repair gene.
Clarkin
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CE
Department of Biochemistry and Molecular Biophysics, University of Pennsylvania, Philadelphia 19104, USA.
Zhang
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H
Weber
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D019313:BRCA1 Protein / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004249:DNA Damage / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D000939:Epitopes; D005260:Female; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects*; D052138:Genes, Neoplasm / Q000528:radiation effects*; D006207:Half-Life; D006801:Humans; D007700:Kinetics; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D016196:S Phase / Q000528:radiation effects; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays
D019313:BRCA1 Protein; D000939:Epitopes; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D003513:Cycloheximide