The LIM homeobox protein mLIM3/Lhx3 induces expression of the prolactin gene by a Pit‐1/GHF‐1‐independent pathway in corticotroph AtT20 cells

FEBS Letters

Girardin, Stephen E¹  Chrétien, Michel²  Benjannet, Suzanne²  Barale, Jean-Christophe¹  Seidah, Nabil G¹ 

[1] Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, 110 Pine Avenue West, Montréal, Qué. H2W 1R7, Canada;Laboratory of Molecular Neuroendocrinology, Clinical Research Institute of Montreal, Montréal, Qué. H2W 1R7, Canada

关键词: mLIM3;    Prolactin;    AtT20 cells;    Promoter;    Pituitary;   

DOI  :  10.1016/S0014-5793(98)00787-X

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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.

【 授权许可】

Unknown