Characterization of tilapia FSH beta gene and analysis of its 5 ' flankingregion

The objective of the current study was to unveil molecular mechanisms under lying transcriptional regulation of the FSH beta gene expression in the pit uitary of tilapia (Oreochromis mossambicus). The full-length sequence of ti lapia FSH beta (tFSH beta) gene was determined. Its transcriptional unit (2 .7 kb) exhibits the conserved genomic organization, i.e. three exons and tw o introns. Primer extension and RT-PCR analysis revealed heterogeneity of t he tFSH beta transcripts, due to alternate mRNA splicing and multiple initi ation sites for transcription. Examination of the 5 ' flanking region (5 ' FR) of the tFSH beta gene identified potential CAAT and TATA promoter proxi mal elements as well as several sequences of cis-acting motifs known to dic tate inducible and tissue-specific transcriptional regulation in other gona dotropin genes. Chimeric constructs containing 1.7 kb of the tFSH beta 5 ' FR fused to a luciferase (LUC) reporter gene were transiently transfected i nto primary culture of tilapia pituitary cells. The tFSH beta -LUC construc t was efficiently expressed under basal conditions and was rapidly induced by GnRH stimulation. Our data indicate that the 5 ' FR contains a functiona l promoter, which is responsive to GnRH treatment. In addition, 5 ' deletio n analysis showed that the 1.7 kb, DNA sequence of the FSH beta 5 ' FR enco mpasses both positive and negative regulatory elements. (C) 2001 Elsevier S cience Inc. All rights reserved.