The LIM-only protein Lmo2 is a bridging molecule assembling an erythroid, DNA-bindinq complex which includes the TAL1, E47, GATA-1 and Ldb1/NLI proteins

The LIM-only protein Lmo2, activated by chromosomal translocations in T-cell leukaemias, is normally expressed in haematopoiesis. It interacts with TAL1 and GATA-1 proteins, but the function of the interaction is unexplained, We now show that in erythroid cells Lmo2 forms a novel DNA-binding complex, with GATA-1, TAL1 and E2A, and the recently identified LIM-binding protein Ldb1/NLI. This oligomeric complex binds to a unique, bipartite DNA motif comprising an E-box, CAGGTG, followed similar to 9 bp downstream by a GATA site, In vivo assembly of the DNA-binding complex requires interaction of all five proteins and establishes a transcriptional transactivating complex, These data demonstrate one function for the LIM-binding protein Ldb1 and establish a function for the LIM-only protein Lmo2 as an obligatory component of an oligomeric, DNA-binding complex which may play a role in haematopoiesis.