Tel1p interacts with Xrs2p via the extreme C terminus of Xrs2p. (A) Tel1p interacts with the C-terminal peptide of Xrs2p. 2FLAG-Tel1p was precipitated with a biotinylated wild-type or mutant C-terminal peptide of Xrs2p. The precipitate (top panel) and the supernatant (bottom panel) were blotted for Tel1p with anti-FLAG antibody. (B) Tel1p interacts with Xrs2p via the C-terminal 20 amino acids of Xrs2p in vivo, and residues K846 and F847 of Xrs2p are required. Strains expressing 2FLAG-Tel1p and the indicated wild-type or mutant Xrs2p-13myc (derived from yYM260, -269, -271, -273, and -274) were immunoprecipitated (IP) with an anti-FLAG antibody. Two percent of the input material and the immunoprecipitate were examined by Western blotting (IB) for Tel1p (anti-FLAG; top panels) and Xrs2p (anti-myc; bottom panels). (C) Kinase-deficient Tel1p retains the ability to interact with Xrs2p. Xrs2p-13myc (anti-myc IP; left) or 2FLAG-Tel1p (anti-FLAG IP; right) was immunoprecipitated from the indicated strains (derived from yYM260, -309, and -312). The input and immunoprecipitate were examined as for panel B. KD refers to the 2FLAG-tel1-D2612A/N2617A allele. “Untag” indicates that the allele was not tagged. Sizes of protein markers (in kDa) are shown on the left.