EEN encodes for a member of a new family of proteins containing an Src homology 3 domain and is the third gene located on chromosome 19p13 that fuses to MLL in human leukemia.

The MLL gene, the closest human homologue to the Drosophila trithorax gene, undergoes chromosomal translocation with a large number of different partner genes in both acute lymphoid and acute myeloid leukemias. We have identified a new partner gene, EEN, fused to MLL in a case of acute myeloid leukemia. The gene is located on chromosome 19p13, where two other MLL partner genes, ENL and ELL/MEN have also been identified. The deduced protein of 368 aa contains a central alpha-helical region and a C-terminal Src homology 3 (SH3) domain most similar to the C-terminal SH3 domain found in the Grb2/Sem-5/Drk family of genes. Sequence analysis of the fusion MLL/EEN transcript in our patient reveals that exon 6 of MLL is fused to the N-terminal end of EEN, a fusion that would create a chimeric protein that includes the major functional domain of EEN. EEN is expressed in a variety of tissue types and encodes a protein of approximately 46 kDa. The EEN protein is the human homologue of a member of a recently described murine SH3 domain-containing protein family. It is also highly related to a putative gene identified in Caenorhabditis elegans, and a number of similar sequences are present in the EST databases of several species.