Premium
The LIM homeobox protein mLIM3/Lhx3 induces expression of the prolactin gene by a Pit‐1/GHF‐1‐independent pathway in corticotroph AtT20 cells
Author(s) -
Girardin Stephen E,
Benjannet Suzanne,
Barale Jean-Christophe,
Chrétien Michel,
Seidah Nabil G
Publication year - 1998
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(98)00787-x
Subject(s) - anterior pituitary , microbiology and biotechnology , biology , homeobox , gene , complementary dna , prolactin cell , prolactin , transcription factor , messenger rna , gene expression , pou domain , electrophoretic mobility shift assay , transfection , genetics , biochemistry , hormone
mLIM3, a member of the LIM homeobox family, was recently demonstrated to be critical for proliferation and differentiation of the pituitary cell lineage. Using a pool of degenerate oligonucleotides we determined the DNA sequence ANNAGGAAA(T/C)GA(C/G)AA as the set preferentially recognized by mLIM3. A nearly identical sequence is found in the prolactin ( PRL ) promoter, within a 15‐mer stretch from nucleotides (nts) −218 to −204 which is highly conserved between human, rat, and bovine. In order to test the hypothesis of a transcriptional effect of mLIM3 on the prolactin promoter, stable transfectants of mLIM3 cDNA in AtT20 tumor cells revealed that PRL mRNA expression was induced in 3 separate stable clones. Gel retardation experiments performed using nuclear extracts isolated from one of the AtT20/mLIM3 stable transfectants revealed affinity towards the 15‐mer element of the PRL promoter. From these results, we propose that the PRL promoter element (nts −218 to −204) could be functional in vivo. Finally, we demonstrate that in AtT20 cells prolactin mRNA expression is not induced by the Pit‐1/GHF‐1 pathway and that growth hormone mRNA is not detected concomitantly with prolactin. We conclude that mLIM3 may play a key role in inducing PRL gene expression in lactotrophs by binding to a conserved motif close to a Pit‐1/GHF‐1 site within the proximal PRL promoter.