The t(8;21)(q22;q22) is the most commonly observed chromosomal translocation in acute myeloid leukemia (AML) patients; it generates the AML1-ETO (AE) fusion protein1–4, which contains the N-terminal 177 amino acids of AML1 [also known as RUNX1 (runt-related transcription factor 1)] fused to nearly the entire ETO protein1–4. Here, RUNX1 is linked to acute myeloid leukemia.