Positive modulator of ATM response to DNA damage. Part of a multisubunit complex that groups tRNA ligases for Arg (RARS1), Asp (DARS1), Gln (QARS1), Ile (IARS1), Leu (LARS1), Lys (KARS1), Met (MARS1) the bifunctional ligase for Glu and Pro (EPRS1) and the auxiliary subunits AIMP1/p43, AIMP2/p38 and EEF1E1/p18 (PubMed:12060739). Can interact simultaneously with MARS1 and EPRS1. Forms a linear complex that contains MARS1, EEF1E1, EPRS1 and AIMP2 that is at the core of the multisubunit complex. Interacts with ATM and ATR. The interaction with ATM, which takes place independently of TP53, is induced by DNA damage that may occur during genotoxic stress or cell growth. The interaction with ATR is enhanced by UV irradiation (By similarity). Cytoplasmic under growth arrest conditions. Translocated into the nucleus when growth resumes at S phase and following DNA damage. By DNA damaging agents, such as UV, adriamycin, actinomycin D and cisplatin.