Rad54: The Motor of Homologous Recombination

Rad54: DNA Translocation The DNA translocation activity (forming positive and negative supercoils) is required for all other Rad54 activities in the cell Mazin et al. 2010

Rad54: Chromatin Remodeling The chromatin remodeling and protein (histone) displacement activities free the DNA for processing by other proteins (such as Rad51 and Rad52) Mazin et al. 2010

Rad54: Rad51 Interaction Rad54 stabilizes the Rad51 nucleoprotein filament and also stimulates stand invasion Mazin et al. 2010

Rad54: Dual Threat Rad54 can both stabilize the Rad51 filament (in the presence of Ca2+) and dissociate Rad51 (in the absence of Ca2+) -Dissociation of Rad51 is a result of the translocation activity Mazin et al. 2010

Rad54: Branch Migration The branch migration activity allows for processing of HR intermediates -Mus81 activation by Rad54 resolves HR intermediates Mazin et al. 2010

The ATPase Motor All Rad54 activities (with the exception of Rad51 stabilization) require the ATPase activity Walker A Box [G,X,G,K,S/T]

The ATPase Motor Structure of the “Walker A Box” -Site of ATP binding and hydrolysis T184 Zebrafish Rad54 C-terminal domain K183 L181 Thoma et al. 2005

Conserved YET Disputed Sequence PCNA Interacting Protein sequence Box (PIP Box) (Burgess et al) OR -DNA binding sequence extending Motif III (Zhang et al) -Both agree this sequence is necessary for ATPase activity

Conserved YET Disputed Sequence Tyrosine and Phenylalanine mutants have shown significant decreases in activity Thoma et al. 2005

Hydropathy Plot No significant hydrophobic residues with some more significant hydrophilic residues -Consistent with a DNA-interacting protein

References