SUMO E3 ligase Mms21 prevents spontaneous DNA damage induced genome rearrangements.

Mms21, a subunit of the Smc5/6 complex, possesses an E3 ligase activity for the Small Ubiquitin-like MOdifier (SUMO). Here we show that the mms21-CH mutation, which inactivates Mms21 ligase activity, causes increased accumulation of gross chromosomal rearrangements (GCRs) selected in the dGCR assay. These dGCRs are formed by non-allelic homologous recombination between divergent DNA sequences mediated by Rad52-, Rrm3- and Pol32-dependent break-induced replication.