FIG. 10.

Models for DSB processing by the MRX complex and Exo1. In wild-type cells, ends are processed by unwinding of ends and endonucleolytic cleavage of the 5′ strand by the Mre11 nuclease. Unwinding could be mediated by the weak unwinding activity of the Mre11 complex or by association with a DNA helicase. In the absence of the MRX complex, Exo1 inefficiently processes the ends. The M*RX complex in cells expressing the mre11-H125N allele is still able to unwind ends, and other nucleases remove the 5′ single-stranded tails.