[en] To study the elements involved in the pituitary specific transcriptional regulation of the tilapia prolactin I gene (tiPRL I), we have cloned and entirely sequenced a 3.4-kb genomic fragment immediately upstream from the first exon. In footprinting experiments, three tilapia sequences are protected from DNase I digestion by rat pituitary extracts (base pair coordinates -643 to -593, -160 to -111, and -73 to -46). Computer analysis of the nucleotide sequence reveals significant homology to mammalian binding sites for Pit-1, a transcription factor that is known to mediate pituitary-specific expression of the PRL genes in mammals. The tiPRL I 5'-flanking sequences can direct transient expression of a linked luciferase reporter gene in transfected rat pituitary cell lines and tilapia pituitary primary cell cultures. Transient expression experiments with 5'-deletion mutants reveal three regulatory regions. Two have a stimulatory effect on transcription and one an inhibitory effect. Electrophoretic mobility-shift assays (EMSA) demonstrate that the rat Pit-1 factor specifically binds to tilapia DNA sequences. Several such tilapia Pit-1 binding sites mediate activation of a linked heterologous promoter in transfected rat and tilapia pituitary cells. As evidenced by EMSA, a Pit-1-like protein is present in tilapia pituitary extracts. All these data point to a high conservation of the molecular mechanisms involved in pituitary-specific expression of the PRL genes in vertebrates.
Research center :
AFFISH-RC - Applied and Fundamental FISH Research Center - ULiège
Disciplines :
Biochemistry, biophysics & molecular biology
Author, co-author :
Poncelet, A. C.
Levavi-Sivan, B.
Muller, Marc ; Université de Liège - ULiège > Département des sciences de la vie > GIGA-R : Biologie et génétique moléculaire
Yaron, Z.
Martial, Joseph ; Université de Liège - ULiège > Département des sciences de la vie > GIGA-R : Biologie et génétique moléculaire
Belayew, A.
Language :
English
Title :
The tilapia prolactin I gene: evolutionary conservation of the regulatory elements directing pituitary-specific expression
Publication date :
1996
Journal title :
DNA and Cell Biology
ISSN :
1044-5498
eISSN :
1557-7430
Publisher :
Mary Ann Liebert, Inc., Larchmont, United States - New York
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