A novel H2A.Z deposition pathway involving the Ku70/Ku80 heterodimer

The Ku heterodimer, consisting of Ku70 and Ku80 subunits, is an evolutionary conserved complex with a prominent raie in NHEJ repair. The Ku heterodimer is a highly abundant chromatin associated complex. How the Ku proteins are recruited to chromatin in the absence of DNA damage is still unknown. Using tandem-affinity purification procedure, we identified the Ku heterodimer as one of the major component of the H2A.Z predeposition complex. Using deletion mapping, we identified the vWA demain of Ku80 as the primary motif responsible for its interaction with H2A.Z/H2B dimers. This interaction is mediated essentially by H2B in the presence of H2A.Z but not in the presence of H2A or H2AX. Analysis of H2A.Z localization in Ku80-/- cells by chromatin immunoprecipitation followed by sequencing shows specific depletion of H2A.Z from promoters but not from enhancers or insulators. Collectively, our data uncover a navel function of the Ku complex in the mechanism of H2A.Z/H2B deposition at promoters.