A. Sela-brown et al., Identification of AUF1 as a parathyroid hormone mRNA 3 '-untranslated region-binding protein that determines parathyroid hormone mRNA stability, J BIOL CHEM, 275(10), 2000, pp. 7424-7429
Parathyroid hormone (PTH) mRNA levels are posttranscriptionally increased b
y hypocalcemia and decreased by hypophosphatemia, and this is mediated by c
ytosolic proteins binding to the PTH mRNA 3'-untranslated region (UTR). The
same proteins are also present in other tissues, such as brain, but only i
n the parathyroid is their binding regulated by calcium and phosphate. The
function of the PTH mRNA 3'-UTR-binding proteins was studied using an in vi
tro degradation assay. Competition for the parathyroid-binding proteins by
excess unlabeled 3'-UTR destabilized the full-length PTR transcript in this
assay, indicating that these proteins protect the RNA from RNase activity.
The PTH RNA 3'-UTR-binding proteins were purified by RNA affinity chromato
graphy of rat brain S-100 extracts. The eluate from the column was enriched
in PTH RNA 3'-UTR binding activity. Addition of eluate to the In vitro deg
radation assay with parathyroid protein extracts stabilized the PTH transcr
ipt. A major band from the eluate at 50 kDa was sequenced and was identical
to AU-rich binding protein (AUF1). Recombinant AUF1 bound the full-length
PTH mRNA and the 3'-UTR. Added recombinant AUF1 also stabilized the PTH tra
nscript in the in vitro degradation assay. Our results show that AUF1 is a
protein that binds to the PTH mRNA 3'-UTR and stabilizes the PTH transcript
.