A conserved cis-acting element in the parathyroid hormone 3 '-untranslatedregion is sufficient for regulation of RNA stability by calcium and phosphate

Calcium and phosphate regulate parathyroid hormone (PTH) gene expression po st-transcriptionally by changes in protein-PTH mRNA 3'-untranslated region (UTR) interactions, which determine PTH mRNA stability. We have identified the protein binding sequence in the PTH mRNA 3'-UTR and determined its func tionality. The protein-binding element was identified by binding, competiti on, and antisense oligonucleotide interference. The sequence was preserved among species suggesting its importance. To study its functionality in the context of another RNA, a 63-base pair cDNA PTH sequence was fused to the g rowth hormone (GN) gene, There is no parathyroid (PT) cell line and therefo re an in vitro degradation assay was used to determine the stability of tra nscripts for PTH, GH, and a chimeric GH-PTH 63 nucleotides with PT cytosoli c proteins. The full-length PTH transcript was stabilized by PT proteins fr om rats fed a low calcium diet and destabilized by proteins from rats fed a low phosphate diet, correlating with PTH mRNA levels in vivo, These PT pro teins did not affect the native GH transcript. However, the chimeric GH tra nscript was stabilized by low calcium PT proteins and destabilized by low p hosphate PT proteins, similar to the PTH full-length transcript. Therefore, we have identified a PTH RNA-protein binding region and shown that it is s ufficient to confer responsiveness to calcium and phosphate in a reporter g ene. This defined element in the PTH mRNA 3'-UTR is necessary and sufficien t for the regulation of PTH mRNA stability by calcium and phosphate.