Phospho-dependent interactions between NBS1 and MDC1 mediate chromatin retention of the MRN complex at sites of DNA damage

• Published in: EMBO reports 2008-08, Vol.9 (8), p.795-801
• Main Authors: Chapman, J Ross, Jackson, Stephen P
• Format: Article
• Language: English
• Subjects: Acid Anhydride Hydrolases; Adaptor Proteins, Signal Transducing; Amino Acid Motifs; Amino Acid Sequence; Animals; Casein Kinase II - genetics; Casein Kinase II - metabolism; Cell cycle; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Cell Line, Tumor; Cellular biology; checkpoint; Chromatin; Chromatin - metabolism; CK2; Deoxyribonucleic acid; DNA; DNA Damage; DNA Repair Enzymes - genetics; DNA Repair Enzymes - metabolism; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Flow Cytometry; HeLa Cells; Humans; Immunoblotting; Immunoprecipitation; Mammals; Mass Spectrometry; MDC1; Mice; Microscopy, Fluorescence; Molecular biology; Molecular Sequence Data; MRE11 Homologue Protein; MRN; NBS1; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Phosphorylation; Protein Binding; Proteins; Scientific Report; Sequence Homology, Amino Acid; Trans-Activators - genetics; Trans-Activators - metabolism
• ISSN: 1469-221X; 1469-3178; 1469-221X
• DOI: 10.1038/embor.2008.103

Mammalian cells respond to DNA double‐strand breaks (DSBs) by recruiting DNA repair and cell‐cycle checkpoint proteins to such sites. Central to these DNA damage response (DDR) events is the DNA damage mediator protein MDC1. MDC1 interacts with several DDR proteins, including the MRE11–RAD50–NBS1 (MRN) complex. Here, we show that MDC1 is phosphorylated on a cluster of conserved repeat motifs by casein kinase 2 (CK2). Moreover, we establish that this phosphorylation of MDC1 promotes direct, phosphorylation‐dependent interactions with NBS1 in a manner that requires the closely apposed FHA and twin BRCT domains in the amino terminus of NBS1. Finally, we show that these CK2‐targeted motifs in MDC1 are required to mediate NBS1 association with chromatin‐flanking sites of unrepaired DSBs. These findings provide a molecular explanation for the MDC1–MRN interaction and yield insights into how MDC1 coordinates the focal assembly and activation of several DDR factors in response to DNA damage.