Figure 1.

Interactions of Rad51 and Hed1 proteins. Sequence comparison of Hed1 and Rad51 in different yeast strains reveals loss of the COOH-terminal region of Hed1 (A), and the NH₂-terminal region of Rad51 (B) in the budding yeast strain Vin13. Protein sequences were retrieved from the Saccharomyces Genome Database (SGD). Multiple sequence alignments were performed with MAFFT version 7 (63), and the results were displayed and edited with GeneDoc (version 2.7.000; https://www.softpedia.com/get/Science-CAD/GeneDoc.shtml). Identical residues are shaded in black. (A) The reported Rad51-interacting region of Hed1 is shaded in yellow. (B) The initial 66 amino acid stretch (Met¹ to Glu⁶⁶) of S. cerevisiae Rad51 is defined as the NH₂-terminal domain (NTD). Three SQ motifs (S²Q, S¹²Q and S³⁰Q) in the NTD and one S¹⁹²Q motif in the ATPase domain are highlighted in red. The methionine (Met⁶⁷) following the NTD is shown in blue. (C) Yeast two-hybrid assay showing interactions between Rad51 fragments and Hed1. Quantitative yeast LacZ assays were performed as described previously (40,41). Hed1 is expressed from pGADT7 vectors (Clontech, USA), whereas in X-LexA the bait protein X is NH₂-terminal to LexA (64) (Supplementary Table S3). Error bars indicate standard deviation between experiments (n ≥ 3, see Supplementary Table S3 for the exact sample sizes). Asterisks indicate significant differences when compared to values of interaction between WT Rad51–LexA and Gal4AD–Hed1, with P values calculated using a two-tailed t-test (*P value < 0.05 and ***P value < 0.001).