Abstract
Actively transcribed regions of the genome are protected by transcription-coupled DNA repair mechanisms, including transcription-coupled homologous recombination (TC-HR). Here we used reactive oxygen species (ROS) to induce and characterize TC-HR at a transcribed locus in human cells. As canonical HR, TC-HR requires RAD51. However, the localization of RAD51 to damage sites during TC-HR does not require BRCA1 and BRCA2, but relies on RAD52 and Cockayne Syndrome Protein B (CSB). During TC-HR, RAD52 is recruited by CSB through an acidic domain. CSB in turn is recruited by R loops, which are strongly induced by ROS in transcribed regions. Notably, CSB displays a strong affinity for DNA:RNA hybrids in vitro, suggesting that it is a sensor of ROS-induced R loops. Thus, TC-HR is triggered by R loops, initiated by CSB, and carried out by the CSB-RAD52-RAD51 axis, establishing a BRCA1/2-independent alternative HR pathway protecting the transcribed genome.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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BRCA1 Protein / genetics
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BRCA1 Protein / metabolism
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BRCA2 Protein / genetics
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BRCA2 Protein / metabolism
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Base Sequence
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Cell Line, Tumor
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DNA / genetics
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DNA / metabolism
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DNA Damage
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DNA Helicases / genetics
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DNA Helicases / metabolism*
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DNA Repair
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DNA Repair Enzymes / genetics
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DNA Repair Enzymes / metabolism*
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HEK293 Cells
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Homologous Recombination*
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Humans
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Poly-ADP-Ribose Binding Proteins / genetics
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Poly-ADP-Ribose Binding Proteins / metabolism*
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Rad51 Recombinase / genetics
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Rad51 Recombinase / metabolism
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Rad52 DNA Repair and Recombination Protein / genetics
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Rad52 DNA Repair and Recombination Protein / metabolism
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Reactive Oxygen Species / metabolism*
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Sequence Homology, Amino Acid
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Transcription, Genetic*
Substances
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BRCA1 Protein
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BRCA1 protein, human
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BRCA2 Protein
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BRCA2 protein, human
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Poly-ADP-Ribose Binding Proteins
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RAD52 protein, human
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Rad52 DNA Repair and Recombination Protein
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Reactive Oxygen Species
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DNA
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Rad51 Recombinase
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DNA Helicases
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ERCC6 protein, human
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DNA Repair Enzymes