In this publication we show that MRE11 interacts directly with the chaperone PIH1D1 in vivo and in vitro. This interaction depends on the PIH1D1 phospho-binding domain (PIH-N) and a CK2 mediated phosphorylation of MRE11 on Ser 688/9 and Ser 558/561. We showed that PIH1D1 is important for the stability of the MRN complex components. In addition we showed that PIH1D1 knockdown also negatively influences the repair of two different MRN dependent repair pathways, namely homologous recombination and the removal of TOP2-adducts from DNA. U2OS cell lines expressing GFP MRE11 WT or GFP MRE11 with Ser 688/9 and/or Ser 558/561 mutated to Alanine. Cellular stress by siRNA transfection decreased the stability of the GFP MRE11 mutated at Ser 688/9 but not of GFP MRE11 WT or GFP MRE11 mutated at Ser 558/561 (observed in multiple clones). These results further establish a role of PIH1D1 in the DNA damage response and indicate that the interaction between PIH1D1 and MRE11 is involved in assembly of the MRN complex