Single Molecule Imaging of Tid1/Rdh54, a Rad54 Homolog That Translocates on Duplex DNA and Can Disrupt

Tid1 protein is important forthe recombinational repair of double-stranded DNA breaksduring meiosis. Tid1 is a member of Swi2/Snf2 family of chro-matin remodeling proteins and shares homology with Rad54.MembersofthisfamilyhydrolyzeATPandpromote1)chroma-tin remodeling, 2) DNA topology alterations, and 3) displace-mentofproteinsfromDNA.Alloftheseactivitiesarepresumedto require translocation of the protein on DNA. Here we usesingle-molecule visualization to provide direct evidence for theabilityofTid1totranslocateonDNA.Tid1translocationisATP-dependent, and the velocities are broadly distributed, with theaveragebeing84 39basepairs/s.Translocationisprocessive,with the average molecule traveling 10,000 base pairs beforepausing or dissociating. Many molecules display simple mono-tonic unidirectional translocation, but the majority displaycomplex translocation behavior comprising intermittentpauses, direction reversals, and velocity changes. Finally, wedemonstrate that translocation by Tid1 on DNA can result indisruption of three-stranded DNA structures. The ability ofTid1 translocation to clear DNA of proteins and to migraterecombination intermediates may be of critical importance forDNA repair and chromosome dynamics.