Characterization of the porcine Lhx3/LIM-3/P-Lim LIM homeodomain transcription factor

Lhx3/LIM-3/P-Lim is a LIM homeodomain transcription factor which is essenti al in mice for the development of anterior and intermediate lobes of the pi tuitary gland. We report the cloning and characterization of porcine Lhx3. The porcine Lhx3 protein exhibits strong similarity to murine Lhx3 within t he amino terminal LIM domains and the homeodomain, however, it is diverged in regions outside these motifs. Expression vectors for porcine Lhx3 activa ted murine and porcine alpha-glycoprotein reporter genes in transfection as says, and recombinant porcine Lhx3 protein specifically bound to a target s ite within the porcine alpha-glycoprotein gene upstream sequence. In additi on, porcine Lhx3 synergistically induced transcription from prolactin enhan cer/promoter reporter genes in cooperation with the Pit-1 pituitary transcr iption factor. Porcine Lhx3 protein interacted with Pit-1 protein in soluti on and also with the LIM domain-binding protein NLI/Lbd1/CLIM. Together, th ese data indicate that many aspects of Lhx3 function in the mammalian pitui tary are conserved and that Lhx3 may be involved in the activation of troph ic hormone genes during early and late stages of pituitary organogenesis. D ivergence in the Lhx3 amino acid sequence between mammalian species may sug gest distinct activities for this protein in some species and may help iden tify important functional domains of this key developmental transcription f actor. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.