The second LIM domain of Lhx3-Lhx4 family: Lhx3 and Lhx4 belong to the LHX protein family, which features two tandem N-terminal LIM domains and a C-terminal DNA binding homeodomain. Members of LHX family are found in the nucleus and act as transcription factors or cofactors. LHX proteins are critical for the development of specialized cells in multiple tissue types, including the nervous system, skeletal muscle, the heart, the kidneys, and endocrine organs, such as the pituitary gland and the pancreas. The LHX3 and LHX4 LIM-homeodomain transcription factors play essential roles in pituitary gland and nervous system development. Although LHX3 and LHX4 share marked sequence homology, the genes have different expression patterns. They play overlapping, but distinct functions during the establishment of the specialized cells of the mammalian pituitary gland and the nervous system. Lhx3 proteins have been demonstrated the ability to directly bind to the promoters/enhancers of several pituitary hormone gene promoters to cause increased transcription.Lhx3a and Lhx3b, whose mRNAs have distinct temporal expression profiles during development, are two isoforms of Lhx3. LHX4 plays essential roles in pituitary gland and nervous system development. In mice, the lhx4 gene is expressed in the developing hindbrain, cerebral cortex, pituitary gland, and spinal cord. LHX4 shows significant sequence similarity to LHX3, particularly to isoforms Lhx3a. In gene regulation experiments, the LHX4 protein exhibits regulation roles towards pituitary genes, acting on their promoters/enhancers. As in other LIM domains, this domain family is 50-60 amino acids in size and shares two characteristic zinc finger motifs. The two zinc fingers contain eight conserved residues, mostly cysteines and histidines, which coordinately bond to two zinc atoms. LIM domains function as adaptors or scaffolds to support the assembly of multimeric protein.
Comment:The two zinc fingers contain eight conserved residues, mostly cysteines and histidines, which coordinately bond to two zinc atoms. The Zn binding residues of LIM domain are highly conserved.
Jiyao W et al.(2023). "The conserved domain database in 2023.",