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Through an RNAi-based screen for previously uncharacterized regulators of genome stability, we have identified the human protein C5orf45 as an important factor in preventing the accumulation of DNA damage in human cells. Here, we functionally characterize C5orf45 as a binding partner of the MRE11-RAD50-NBS1 (MRN) damage-sensing complex. Hence, we rename C5orf45 as MRNIP for MRN-interacting protein (MRNIP). We find that MRNIP is rapidly recruited to sites of DNA damage. Cells depleted of MRNIP display impaired chromatin loading of the MRN complex, resulting in reduced DNA end resection and defective ATM-mediated DNA damage signaling, a reduced ability to repair DNA breaks, and radiation sensitivity. Finally, we show that MRNIP phosphorylation on serine 115 leads to its nuclear localization, and this modification is required for MRNIP's role in promoting genome stability. Collectively, these data reveal that MRNIP is an important component of the human DNA damage response.

Original publication




Journal article


Cell Rep

Publication Date





2565 - 2575


Ataxia Telangiectasia Mutated Proteins, Carrier Proteins, Checkpoint Kinase 2, Chromatin, DNA Breaks, Double-Stranded, DNA Damage, DNA Repair, HCT116 Cells, HEK293 Cells, HeLa Cells, Humans, Multiprotein Complexes, Nuclear Proteins, Protein Binding, Radiation Tolerance, Radiation, Ionizing, Sequence Homology, Amino Acid, Signal Transduction