Role of the LIM domains in DNA recognition by the Lhx3 neuroendocrine transcription factor

LIM homeodomain transcription factors regulate many aspects of development in multicellular organisms. Such factors contain two LIM domains in their a mino terminus and a DNA-binding homeodomain. To better understand the mecha nism of gene regulation by these proteins, we studied the role of the LIM d omains in DNA interaction by Lhx3, a protein that is essential for pituitar y development and motor neuron specification in mammals. By site selection, we demonstrate that Lhx3 binds at high affinity to an AT-rich consensus DN A sequence that is similar to sequences located within the promoters of som e pituitary hormone genes. The LW domains reduce the affinity of DNA bindin g by Lhx3, but do not affect the specificity. Lhx3 preferentially binds to the consensus site as a monomer with minor groove contacts. The Lhx3 bindin g consensus site confers Lhx3-dependent transcriptional activation to heter ologous promoters. Further, DNA molecules containing the consensus Lhx3 bin ding site are bent to similar angles in complexes containing either wild ty pe Lhx3 or Lhx3 lacking LIM domains. These data are consistent with Lhx3 ha ving the properties of an architectural transcription factor. We also propo se that there are distinct classes of LIM homeodomain transcription factors in which the LIM domains play different roles in modulating interactions w ith DNA sites in target genes. (C) 2001 Elsevier Science B.V. All rights re served.