DNA DOUBLE-STRAND BREAK REPAIR BY THE MRE11/RAD50 COMPLEX IN T4 PHAGE

Abstract

The T4 phage proteins Mre11 and Rad50, also known as gp46 and gp47, are responsible for the detection of DNA double-strand break and initiation of its repair. Mre11 carries out the nuclease and strand annealing activities at the site of damage while Rad50, an ATPase, regulates the nuclease activity of Mre11. Mutation in either protein can lead to the loss of DNA repair function and, in humans, this leads to various forms of cancer, neurological disorders, and immunological deficiencies. Although crystal structures of Mre11-Rad50 complex have been reported, the precise mechanism of communication between the two partner proteins in executing the DNA repair remains poorly understood. We carried out in vitro biophysical characterization of the solution behavior of the T4 Mre11/Rad50 proteins using hydrogen-deuterium exchange followed by mass spectrometry. Based on our study, we propose a new model for domain arrangement of T4Mre11/Rad50 proteins in the complex. Our model is found to differ from the models proposed so far.