Binds to the LIM domain of a wide variety of LIM domain-containing transcription factors. May regulate the transcriptional activity of LIM-containing proteins by determining specific partner interactions. Plays a role in the development of interneurons and motor neurons in cooperation with LHX3 and ISL1. Acts synergistically with LHX1/LIM1 in axis formation and activation of gene expression. Acts with LMO2 in the regulation of red blood cell development, maintaining erythroid precursors in an immature state. Interacts with ESR1 (By similarity). Forms homodimers and heterodimers. Interacts with and activates LHX1/LIM1. Interacts with the LIM domains of ISL1 and LMO2. Can assemble in a complex with LMO2 and TAL1/SCL but does not interact with TAL1/SCL directly. Strongly interacts with the LIM2 domain of LMX1A and more weakly with the LIM1 domain. Homodimerization is not required for, and does not effect, LMX1A-binding. Component of a nuclear TAL-1 complex composed at least of CBFA2T3, LDB1, TAL1 and TCF3. Interacts with LHX6 and LHX9. At neuronal promoters, forms a complex with LHX3 involved in the specification of interneurons, in motor neurons, it is displaced by ISL1 to form a ternary complex in which ISL1 contacts both LHX3 and LDB1. Interacts with SLK; leading to negatively regulate SLK kinase activity (PubMed:19675209). Interacts with YWHAZ (By similarity). Interacts with PRDM1/BLIMP1 (By similarity). Colocalizes with SLK at leading edges (PubMed:19675209). Expression overlaps that of LIM domain-containing proteins. Expressed widely in the embryo with highest expression in several regions of the brain the central nervous system ganglia. Also expressed in fetal liver, lung, kidney, thymus and olfactory epithelium. Expressed in multiple adult tissues including heart, brain, liver, kidney, testis, lung and muscle and a diverse range of neuronal cell types, with expression highest in the pituitary gland and skin. Expressed in both embryonic and adult hemopoietic cells, including the erythroid lineage. The dimerization domain is located in the N-terminus. Ubiquitinated by RLIM/RNF12, leading to its degradation by the proteasome. Due to intron retention. Lacks LIM-binding domain. Lacks ability to activate LIM domain-dependent transcription. Belongs to the LDB family.