Abstract
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.
Keywords:
DNA breaks; DNA repair; cell cycle; homologous chromosome contact; homologous recombination; nuclear architecture.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Ataxia Telangiectasia Mutated Proteins
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism
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Chromosomes, Human / genetics*
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DNA Breaks, Double-Stranded / radiation effects*
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DNA Restriction Enzymes / genetics
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DNA Restriction Enzymes / metabolism
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DNA-Activated Protein Kinase / genetics
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DNA-Activated Protein Kinase / metabolism
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism
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Fibroblasts / cytology
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Fibroblasts / metabolism
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Fibroblasts / radiation effects*
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Gene Expression Regulation
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Humans
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In Situ Hybridization, Fluorescence
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Primary Cell Culture
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Radiation, Ionizing
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Recombinational DNA Repair / radiation effects*
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Resting Phase, Cell Cycle / genetics*
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Thyroid Gland / cytology
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Thyroid Gland / metabolism
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Thyroid Gland / radiation effects*
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Time Factors
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Tissue Culture Techniques
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Tumor Suppressor Proteins / genetics
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Tumor Suppressor Proteins / metabolism
Substances
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Cell Cycle Proteins
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DNA-Binding Proteins
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Nuclear Proteins
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Tumor Suppressor Proteins
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ATM protein, human
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Ataxia Telangiectasia Mutated Proteins
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DNA-Activated Protein Kinase
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PRKDC protein, human
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Protein Serine-Threonine Kinases
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DNA Restriction Enzymes