CALCITONIN INCREASES TRANSCRIPTION OF PARATHYROID HORMONE-RELATED PROTEIN VIA CAMP

Transcriptional regulation of the human parathyroid hormone-related pr otein (PTHrP) gene by calcitonin was examined in a lung cancer line (B EN cells). Northern analysis demonstrated that calcitonin caused a rap id 4.5-fold elevation in PTHrP mRNA. Transient transfection of a const ruct containing 11 19 base pairs of the human PTHrP gene 5' to the ATG start site of translation, fused to the CAT reporter sequence, was us ed to demonstrate a five-fold increase in transcription by calcitonin. Similar increases were also observed when transfected cells were expo sed to a number of cAMP agonists including forskolin, as well as isobu tyl-methylxanthine. A putative cAMP responsive element (5'-TGACTTCA-3' ) present within exon 4 was placed upstream of the heterologous SV40 p romoter. Expression of this construct was elevated 4.5-fold in respons e to calcitonin and 7-fold in response to forskolin. Similar responses to calcitonin occurred with a smaller construct (pZMR30) containing 5 30 bp of sequence upstream of the ATG start site. Thus we postulate th at calcitonin acts at least partially via cAMP through this element in exon 4 of the human PTHrP gene.