Part of the TTT complex that is required to stabilize protein levels of the phosphatidylinositol 3-kinase-related protein kinase (PIKK) family proteins (By similarity). Required for telomere length regulation and telomere position effect. Regulates telomere length and participates in gene silencing at subtelomeric regions. Binds to telomeric DNA repeats. Component of the TTT complex composed of TEL2, TTI1 and TTI2. Interacts with TTI1 and TTI2. Present with 638 molecules/cell in log phase SD medium. Belongs to the TEL2 family.