Supplementary Figure 1: Structure of the human and yeast Rad50 hook and coiled-coil domains.

(a) Analytical ultracentrifuge data of the Zn-free (bottom left) and –bound Rad50HCC182 constructs (bottom right). (b) Stereoview of the section of the electron density map of Rad50HCC182. The 2.8 Å experimental map contoured at 1.2 I/σ was generated with phases from derived Se-Met anomalous scattering. (c) Sequence alignment of Rad50 homologs. Secondary structures of the coiled-coil domain of HsRad50 are represented above the sequence. Secondary structures of PfRad50 are shown below the sequence of PfRad50. Conserved residues in Rad50 proteins are marked with a yellow box. Mutations identified in breast cancer patients are marked with a blue star. Residues involved in dimerization are marked with a violet square. Rad50 hook mutant suppressors²⁰ are marked with a green triangle. Every tenth residue is marked with a black circle. (d-e) A model for ScRad50 apex dimer. (d) The model was generated using the program Modeller (Sali, A. & Blundell, T.L. Comparative protein modelling by satisfaction of spatial restraints. J. Mol. Biol. 234, 779–815 (1993)) based on human Rad50 apex structure. Close up view of the hook interface of ScRad50 shown in the same orientation as in Fig. 2a. (e) Close up view of the hook and coiled-coil interfaces of ScRad50. The view is orthogonal from that of Supplementary Fig.1d. (f) Close up view of the coiled-coil interface of ScRad50.