mirin is a potent mrn complex inhibitor. mirin inhibits mre11-associated exonuclease activity, rather than alters dna-binding or mrn complex formation. moreover, mirin prevents mrn-dependent activation of atm in response to dna double-strand breaks, with an ic50 value of 12 μm. the mrn complex acts as a dna damage sensor, responsible for maintaining genome stability during dna replication, promoting homology-dependent dna repair and activating atm. the mrn-atm pathway plays an essential role in sensing and signaling from dna double-strand breaks.1. dupré a, boyer-chatenet l, sattler rm, et al. a forward chemical genetic screen reveals an inhibitor of the mre11-rad50-nbs1 complex. nature chemical biology, 2008, 4(2): 119-125.