THE LIM-ONLY PROTEIN LMO2 IS A BRIDGING MOLECULE ASSEMBLING AN ERYTHROID, DNA-BINDINQ COMPLEX WHICH INCLUDES THE TAL1, E47, GATA-1 AND LDB1NLI PROTEINS/

The LIM-only protein Lmo2, activated by chromosomal translocations in T-cell leukaemias, is normally expressed in haematopoiesis. It interac ts 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 iden tified LIM-binding protein Ldb1/NLI. This oligomeric complex binds to a unique, bipartite DNA motif comprising an E-box, CAGGTG, followed si milar to 9 bp downstream by a GATA site, In vivo assembly of the DNA-b inding complex requires interaction of all five proteins and establish es a transcriptional transactivating complex, These data demonstrate o ne function for the LIM-binding protein Ldb1 and establish a function for the LIM-only protein Lmo2 as an obligatory component of an oligome ric, DNA-binding complex which may play a role in haematopoiesis.