Cell-specific and regulator-induced promoter usage and messenger ribonucleic acid splicing for parathyroid hormone-related protein.

Abstract

PTH-related protein (PTHrP) is the principle mediator of the syndrome of humoral hypercalcemia of malignancy and has potential paracrine actions on smooth muscle, epithelial cell growth, and placental calcium transport. The human PTHrP gene is complex: a combination of three promoters, one 5' alternative splicing event and alternative 3' splicing, which produces three PTHrP isoforms (139, 141, or 173 amino acids), results in multiple PTHrP messenger RNA (mRNA) species. We employed the RT-PCR technique to identify promoter usage and splicing patterns in a range of human cell lines. Cell line-specific utilization of the promoters and the 3' alternative splicing pathways was detected among bone, breast, kidney, and lung cell lines, although each cell line could potentially produce the three PTHrP isoforms. We also determined whether some of the known regulators of PTHrP differentially modulate promoter usage or splicing patterns. Dexamethasone decreased the abundance of each of the alternative mRNA species. In contrast, epidermal growth factor and transforming growth factor-beta treatment increased the abundance of each PTHrP mRNA species, with particularly marked effects on promoter 1- and promoter 2-initiated transcripts, especially those containing exon VII or VIII. Epidermal growth factor treatment was found to alter PTHrP splicing patterns in a manner consistent with increased transcription from promoters 1 and 2 and stabilization of exon VII- and IX-containing transcripts.

Transcriptional regulation of parathyroid hormone-related protein promoter P3 by ETS-1 in adult T-cell leukemia/lymphoma

“…These results support a cooperative effect of MAPK Mek-1 with the downstream transcription factor Ets-1 in the transcriptional activation of PTHrP P3 and suggest events occurred through a specific Ets-binding site. 19,21 P3 promoter usage was favored over P2 in HTLV-1-infected cells (RV-ATL, MT-2 and SLB-1) expressing the highest PTHrP and lowest tax/rex mRNA copy numbers whereas the converse was observed in cells (Hut-102 and HT1-RV) expressing low PTHrP and high tax/rex mRNA. The latter finding may be explained by a variety of simple or combined mechanistic actions of Tax or Rex on transcriptional or post-transcriptional regulation of PTHrP gene expression.…”

“…P1 and P3 contain a typical TATA box, [16][17][18] while P2 is a GC-rich promoter region. 19 Previous evaluation of PTHrP alternative promoter usage by qualitative 20,21 and quantitative reverse transcription (RT)-PCR 22 revealed that P3-initiated transcripts were detectable at high levels in most tumors and cell lines examined, including the (HTLV-1)-positive cell line MT-2, whereas P1 or P2-derived transcripts were not detected or expressed only in a subset of tumors.…”

PTHrP Gene Expression in Cancer: Do All Paths Lead to Ets?

“…9,[16][17][18][19][20] Southby of the Melbourne group published a series of RT-PCR-based studies reporting alternative promoter usage in cell lines as well as in breast, lung, parathyroid, and renal neoplasms. 18,21 These authors concluded that P3-derived transcripts were present in all samples, whereas combined P2/P3 usage was prevalent in malignant breast and bone tumorderived lines. Substantial P1 usage was infrequent and generally limited to cell lines and tumors of squamous cell origin.…”

“…21,78 To date, a single regulatory element has been identified in the region upstream of P1. Chilco et al identified a cAMP-responsive element (CRE) located −80bp [−3302 to −3295] upstream of the start of exon 1, suggesting that this motif may be part of the core promoter.…”

“…86,91,108 Southby and colleagues showed that PTHrP 1-141 mRNA had the shortest half-life (approximately 30 minutes) among the three isoforms, whereas 1-173 mRNA was the most stable, with a half-life of up to several hours. 21 The halflife of PTHrP mRNA can also be increased in keratinocytes and squamous carcinoma cell lines by stimulation with TGF-β109-111 and epidermal growth factor (EGF). 112 In HTLV-1-infected cell lines, interleukin-2 (IL-2) 113 also stabilized PTHrP mRNA.…”