Structural mechanism of endonucleolytic processing of blocked DNA ends and hairpins by Mre11-Rad50

Gut, Fabian; Kaeshammer, Lisa; Lammens, Katja; Bartho, Joseph D.; Boggusch, Anna-Maria; Logt, Erik van de; Kessler, Brigitte and Hopfner, Karl-Peter (2022): Structural mechanism of endonucleolytic processing of blocked DNA ends and hairpins by Mre11-Rad50. In: Molecular Cell, Vol. 82, No. 18: pp. 3513-3522

Abstract

DNA double-strand breaks (DSBs) threaten genome stability and are linked to tumorigenesis in humans. Repair of DSBs requires the removal of attached proteins and hairpins through a poorly understood but phys-iologically critical endonuclease activity by the Mre11-Rad50 complex. Here, we report cryoelectron micro-scopy (cryo-EM) structures of the bacterial Mre11-Rad50 homolog SbcCD bound to a protein-blocked DNA end and a DNA hairpin. The structures reveal that Mre11-Rad50 bends internal DNA for endonucleolytic cleavage and show how internal DNA, DNA ends, and hairpins are processed through a similar ATP-regulated conformational state. Furthermore, Mre11-Rad50 is loaded onto blocked DNA ends with Mre11 pointing away from the block, explaining the distinct biochemistries of 3'-> 5' exonucleolytic and endonucleolytic incision through the way Mre11-Rad50 interacts with diverse DNA ends. In summary, our results unify Mre11-Rad50's enigmatic nuclease diversity within a single structural framework and reveal how blocked DNA ends and hairpins are processed.

• Item Type: Journal article
• Faculties: Chemistry and Pharmacy > Department of Pharmacy; Chemistry and Pharmacy > Department of Biochemistry
• Subjects: 500 Science > 540 Chemistry
• ISSN: 1097-2765
• Language: English