The first LIM domain of Lhx3a: Lhx3a is a member of 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. Lhx3a is one of the two isoforms of Lhx3. The Lhx3 gene is expressed in the ventral spinal cord, the pons, the medulla oblongata, and the pineal gland of the developing nervous system during mouse embryogenesis, and transcripts are found in the emergent pituitary gland. Lhx3 functions in concert with other transcription factors to specify interneuron and motor neuron fates during development. Lhx3 proteins have been demonstrated to directly bind to the promoters of several pituitary hormone gene promoters. The Lhx3 gene encodes two isoforms, LHX3a and LHX3b that differ in their amino-terminal sequences, where Lhx3a has longer N-terminal. They show differential activation of pituitary hormone genes and distinct DNA binding properties. In human, Lhx3a trans-activated the alpha-glycoprotein subunit promoter and genes containing a high-affinity Lhx3 binding site more effectively than the hLhx3b isoform. In addition, hLhx3a induce transcription of the TSHbeta-subunit gene by acting on pituitary POU domain factor, Pit-1, while hLhx3b does not. 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.",