Homologous chromosomes move and rapidly initiate contact at the sites of double-strand breaks in genes in G₀-phase human cells.
We recently reported that homologous chromosomes make contact at the sites of double-strand breaks (DSBs) induced by ionizing radiation (IR) and the restriction endonuclease I-PpoI in G₀/G₁-phase somatic human cells. The contact involves short segments of homologous chromosomes and is centered on a DSB that occurs in a gene; contact does not occur at a DSB in intergenic DNA. Contact between homologous chromosomes is abrogated by inhibition of transcription and requires the kinase activity of ATM, but not DNA-PK. Here, we report additional insights into the mechanism underlying this novel phenomenon. We identify four patterns of homologous chromosome contact, and show that contact between homologous arms, but not centrosomes, is induced by IR. Significantly, we demonstrate that contact is induced by IR in non-proliferating, G₀-phase human cells derived from tissue explants. Finally, we show that contact between homologous chromosomes is detectable as early as 5 min after IR. These results point to the existence of a mechanism that rapidly localizes homologous chromosome arms at sites of DSBs in genes in G₀-phase human cells.
Department of Pathology and Laboratory Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
Manoj
M
Gandhi
Viktoria N
VN
Evdokimova
Karen T
KT
Cuenco
Christopher J
CJ
Bakkenist
Yuri E
YE
Nikiforov
D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002877:Chromosomes, Human / Q000235:genetics*; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects*; D004262:DNA Restriction Enzymes / Q000235:genetics / Q000378:metabolism; D051747:DNA-Activated Protein Kinase / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D005786:Gene Expression Regulation; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011839:Radiation, Ionizing; D059767:Recombinational DNA Repair / Q000528:radiation effects*; D016192:Resting Phase, Cell Cycle / Q000235:genetics*; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D013997:Time Factors; D046509:Tissue Culture Techniques; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D004262:DNA Restriction Enzymes
DNA breaks; DNA repair; cell cycle; homologous chromosome contact; homologous recombination; nuclear architecture