Estrogen receptor α-mediated transcription induces cell cycle-dependent DNA double-strand breaks.
Prolonged exposure to estrogen increases breast cancer risk. Estrogen is known to induce chromosomal aberrations, yet the mechanisms by which estrogen promotes genomic instability are not fully understood. Here, we show that exposure of MCF-7 cells to 17β-estradiol (E2) induces DNA double-strand breaks (DSBs), as determined by the formation of γH2AX foci. Foci formation was dependent upon estrogen receptor-α (ERα) and the catalytic activity of the type II topoisomerase, topoisomerase IIβ (topoIIβ). Moreover, we show by chromatin immunoprecipitation that topoIIβ-dependent E2-induced γH2AX localizes to the promoter of the estrogen-inducible gene, trefoil factor 1. E2-induced foci were associated with cyclin A expression and inhibited by pre-incubation with the DNA polymerase inhibitor aphidicolin suggesting that E2-induced DSBs are mediated by progression through S phase. Furthermore, E2-induced γH2AX foci colocalized with Rad51, suggesting that E2-induced DSBs are repaired by homologous recombination. We propose that DNA DSBs formed by the strand-cleaving activity of the topoIIβ-DNA cleavage complex at estrogen-inducible genes can present a barrier to DNA replication, leading to persistent DNA DSBs in ERα-positive breast cancer cells.
Department of Biochemistry and Molecular Biology, Southern Alberta Cancer Research Institute, University of Calgary, Calgary, Alberta, Canada.
Laura M
LM
Williamson
Susan P
SP
Lees-Miller
D064007:Ataxia Telangiectasia Mutated Proteins; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects*; D004261:DNA Replication / Q000528:radiation effects; D004250:DNA Topoisomerases, Type II / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004967:Estrogens / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006657:Histones / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051135:Rad51 Recombinase / Q000235:genetics / Q000378:metabolism; D011839:Radiation, Ionizing; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D004967:Estrogens; C468783:H2AX protein, human; D006657:Histones; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins; D004958:Estradiol; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D051135:Rad51 Recombinase; D004250:DNA Topoisomerases, Type II