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Department of Zoology, The University of Hong Kong, Hong Kong SAR
To whom requests for reprints should be addressed at 1 5N-12, Kadoorie Biological Science Building, The University of Hong Kong, Hong Kong. E-mail: fcleung{at}hkucc.hku.hk
A 1727-bp fragment of 5'-flanking region of chicken growth hormone (cGH) gene has been cloned and sequenced. Various lengths of the 5'-flanking region (122 to 1775 bp) was linked to a luciferase reporter gene, and its transcriptional regulation was examined by an in vitro transient transfection coupled with luciferase assay. Our results demonstrated that pituitary-specific transcription factor, Pit-1, is necessary and sufficient to confer a strong tissue-specific expression. Co-transfection with goldfish or chicken Pit-1 expression vectors significantly restored the luciferase expression in HeLa cells. Site-directed mutagenesis and mobility gel-shift assays further confirmed the position of the Pit-1 binding site at 113/104. Moreover, a repressive thyroid hormone response element (TRE) was identified at 137/74, and we propose that interactions between the TRE and Pit-1 sites may be required for its repressive effect.
Key Words: cGH 5'-flanking region Pit-1 TRE luciferase assay
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