Structure of Yin Yang 1 oligomers that cooperate with RuvBL1-RuvBL2 ATPases.

Yin Yang 1 (YY1) is a transcription factor regulating proliferation and differentiation and is involved in cancer development. Oligomers of recombinant YY1 have been observed before, but their structure and DNA binding properties are not well understood. Here we find that YY1 assembles several homo-oligomeric species built from the association of a bell-shaped dimer, a process we characterized by electron microscopy. Moreover, we find that YY1 self-association also occurs in vivo using bimolecular fluorescence complementation. Unexpectedly, these oligomers recognize several DNA substrates without the consensus sequence for YY1 in vitro, and DNA binding is enhanced in the presence of RuvBL1-RuvBL2, two essential AAA+ ATPases. YY1 oligomers bind RuvBL1-RuvBL2 hetero-oligomeric complexes, but YY1 interacts preferentially with RuvBL1. Collectively, these findings suggest that YY1-RuvBL1-RuvBL2 complexes could contribute to functions beyond transcription, and we show that YY1 and the ATPase activity of RuvBL2 are required for RAD51 foci formation during homologous recombination.