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Human Mre11-Nbs1 complex
Structural highlights
DiseaseMRE11_HUMAN Hereditary breast and ovarian cancer syndrome;Ataxia-telangiectasia-like disorder. The disease is caused by mutations affecting the gene represented in this entry. Defects in MRE11A can be a cause of nephronophthisis-related ciliopathies (NPHP-RC), a group of recessive diseases that affect kidney, retina and brain. A homozygous truncating mutation MRE11A has been found in patients with cerebellar vermis hypoplasia, ataxia and dysarthria. FunctionMRE11_HUMAN Component of the MRN complex, which plays a central role in double-strand break (DSB) repair, DNA recombination, maintenance of telomere integrity and meiosis. The complex possesses single-strand endonuclease activity and double-strand-specific 3'-5' exonuclease activity, which are provided by MRE11A. RAD50 may be required to bind DNA ends and hold them in close proximity. This could facilitate searches for short or long regions of sequence homology in the recombining DNA templates, and may also stimulate the activity of DNA ligases and/or restrict the nuclease activity of MRE11A to prevent nucleolytic degradation past a given point. The complex may also be required for DNA damage signaling via activation of the ATM kinase. In telomeres the MRN complex may modulate t-loop formation. Publication Abstract from PubMedThe DNA double-strand break repair complex Mre11-Rad50-Nbs1 (MRN) detects and nucleolytically processes DNA ends, activates the ATM kinase, and tethers DNA at break sites. How MRN can act both as nuclease and scaffold protein is not well understood. The cryo-EM structure of MRN from Chaetomium thermophilum reveals a 2:2:1 complex with a single Nbs1 wrapping around the autoinhibited Mre11 nuclease dimer. MRN has two DNA-binding modes, one ATP-dependent mode for loading onto DNA ends and one ATP-independent mode through Mre11's C terminus, suggesting how it may interact with DSBs and intact DNA. MRNs two 60-nm-long coiled-coil domains form a linear rod structure, the apex of which is assembled by the two joined zinc-hook motifs. Apices from two MRN complexes can further dimerize, forming 120-nm spanning MRN-MRN structures. Our results illustrate the architecture of MRN and suggest how it mechanistically integrates catalytic and tethering functions. Cryo-EM structure of the Mre11-Rad50-Nbs1 complex reveals the molecular mechanism of scaffolding functions.,Rotheneder M, Stakyte K, van de Logt E, Bartho JD, Lammens K, Fan Y, Alt A, Kessler B, Jung C, Roos WP, Steigenberger B, Hopfner KP Mol Cell. 2022 Dec 20:S1097-2765(22)01138-8. doi: 10.1016/j.molcel.2022.12.003. PMID:36577401[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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