Required for checkpoint signaling after DNA damage. Required for ATR expression, possibly by stabilizing the protein. Interacts with ATR (By similarity). Heterodimer with ATR. The heterodimer binds the RPA complex and is then recruited to single-stranded DNA. Interacts with CEP164 (via N-terminus). Interacts with CINP. Redistributes to discrete nuclear foci upon DNA damage. Ubiquitous. The EEXXXDDL motif is required for the interaction with catalytic subunit PRKDC and its recruitment to sites of DNA damage. Phosphorylated by ATR. Belongs to the ATRIP family. The gene for this protein is either identical to or adjacent to that of TREX1. Some of the mRNAs that encode ATRIP also encode TREX1 in another reading frame. Truncated N-terminus.