Abstract
Interstrand DNA cross-links (ICLs) block both replication and transcription, and are commonly repaired by the Fanconi anemia (FA) pathway. However, FA-independent repair mechanisms of ICLs remain poorly understood. Here we report a previously uncharacterized protein, SAN1, as a 5' exonuclease that acts independently of the FA pathway in response to ICLs. Deletion of SAN1 in HeLa cells and mouse embryonic fibroblasts causes sensitivity to ICLs, which is prevented by re-expression of wild type but not nuclease-dead SAN1. SAN1 deletion causes DNA damage and radial chromosome formation following treatment with Mitomycin C, phenocopying defects in the FA pathway. However, SAN1 deletion is not epistatic with FANCD2, a core FA pathway component. Unexpectedly, SAN1 binds to Senataxin (SETX), an RNA/DNA helicase that resolves R-loops. SAN1-SETX binding is increased by ICLs, and is required to prevent cross-link sensitivity. We propose that SAN1 functions with SETX in a pathway necessary for resistance to ICLs.
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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Animals
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DNA Damage / genetics*
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DNA Helicases / metabolism
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DNA Repair / physiology*
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Enzyme Assays
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Exodeoxyribonucleases / genetics
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Exodeoxyribonucleases / isolation & purification
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Exodeoxyribonucleases / metabolism*
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Fanconi Anemia Complementation Group D2 Protein / genetics
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Fanconi Anemia Complementation Group D2 Protein / metabolism
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Female
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Fibroblasts
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Gene Knockdown Techniques
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Gene Knockout Techniques
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HEK293 Cells
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HeLa Cells
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Humans
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Male
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Mice
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Mice, Knockout
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Multifunctional Enzymes
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RNA Helicases / metabolism*
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RNA, Small Interfering / metabolism
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Recombinant Proteins / genetics
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Recombinant Proteins / isolation & purification
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Recombinant Proteins / metabolism
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Signal Transduction / genetics
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Trans-Activators / genetics
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Trans-Activators / isolation & purification
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Trans-Activators / metabolism*
Substances
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FANCD2 protein, human
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Fancd2 protein, mouse
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Fanconi Anemia Complementation Group D2 Protein
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Multifunctional Enzymes
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RNA, Small Interfering
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Recombinant Proteins
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Trans-Activators
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Exodeoxyribonucleases
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FAM120B protein, human
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Fam120b protein, mouse
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SETX protein, human
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SETX protein, mouse
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DNA Helicases
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RNA Helicases