Different versions of murine Dot1a and Dot1b were expressed as GAL4-DB fusions (1-14) and tested for their ability to interact with various GAL4-AD-AF9 fusions (15-17) in yeast strain AH109. Interaction between any two fusions was identified by the activation ofthethreereporters,resultingintheAde+ His+ and Mel1+ phenotype. Presence(+)or absence (−) of interaction is shown, with +, ++, and +++ indicating the weak, modest, and strong interactions, respectively. 1–12, Dot1a fusions: full-length (1), deletion of the putative leucine zipper, aa 576–597 (2), 2–95 (3), 96–1222 (4), 1223–1540 (5), 417–1222 (6), 417–478 (7), 479–659 (8), 660–828 (9), 829–972 (10), 1112–1222 (11), and 417–828 (12). 2–308 of Dot1b corresponding to 96–416 of Dot1a deleted 322–335 (13). Dot1b corresponding to 96–1222 of Dot1a deleted 322–335 (14). 15–17: AF9 fusions: full-length (15), 339–557 (16), 397–557 (17). Gray, aa 322–335 of Dot1a. Black, leucine zipper motifs. ND, not determined.