Regulator of the DNA damage response (DDR). Part of the TTT complex that is required to stabilize protein levels of the phosphatidylinositol 3-kinase-related protein kinase (PIKK) family proteins. The TTT complex is involved in the cellular resistance to DNA damage stresses, like ionizing radiation (IR), ultraviolet (UV) and mitomycin C (MMC). Together with the TTT complex and HSP90 may participate in the proper folding of newly synthesized PIKKs. Component of the TTT complex composed of TELO2, TTI1 and TTI2. Interacts with TELO2 and TTI1 (PubMed:20801936, PubMed:20810650). Interacts with WAC; WAC positively regulates MTOR activity by promoting the assembly of the TTT complex and the RUVBL complex composed of RUVBL1 and RUVBL2 into the TTT-RUVBL complex which leads to the dimerization of the mTORC1 complex and its subsequent activation (PubMed:26812014). The disease is caused by variants affecting the gene represented in this entry. Belongs to the TTI2 family.