KSRP-PMR1-exosome association determines parathyroid hormone mRNA levels and stability in transfected cells

Morris Nechama,Osnat Bell,Yong Peng,Roberto Gherzi,Tally Naveh-Many,Daniel R Schoenberg,Paola Briata

doi:10.1186/1471-2121-10-70

Abstract

BackgroundParathyroid hormone (PTH) gene expression is regulated post-transcriptionally through the binding of the trans-acting proteins AU rich binding factor 1 (AUF1), Upstream of N-ras (Unr) and KH-type splicing regulatory protein (KSRP) to an AU rich element (ARE) in PTH mRNA 3'-UTR. AUF1 and Unr stabilize PTH mRNA while KSRP, recruiting the exoribonucleolytic complex exosome, promotes PTH mRNA decay.ResultsPTH mRNA is cleaved by the endoribonuclease polysomal ribonuclease 1 (PMR1) in an ARE-dependent manner. Moreover, PMR1 co-immunoprecipitates with PTH mRNA, the exosome and KSRP. Knock-down of either exosome components or KSRP by siRNAs prevents PMR1-mediated cleavage of PTH mRNA.ConclusionPTH mRNA is a target for the endonuclease PMR1. The PMR1 mediated decrease in PTH mRNA levels involves the PTH mRNA 3'-UTR ARE, KSRP and the exosome. This represents an unanticipated mechanism by which the decay of an ARE-containing mRNA is facilitated by KSRP and is dependent on both the exosome and an endoribonuclease.

Highlights

Parathyroid hormone (PTH) gene expression is regulated post-transcriptionally through the binding of the trans-acting proteins AU rich binding factor 1 (AUF1), Upstream of Nras (Unr) and KH-type splicing regulatory protein (KSRP) to an AU rich element (ARE) in PTH mRNA 3'-untranslated region (UTR)
PMR60 decreases PTH mRNA and protein levels in transfected HEK293 cells by promoting ARE-dependent PTH mRNA decay Using an antibody to Xenopus polysomal ribonuclease 1 (PMR1) we identified the mammalian PMR1 ortholog in rat parathyroid, rat liver, and human HEK293 cells
HEK293 cells were transiently co-transfected with plasmids expressing the endoribonuclease together with either rat (r) or human (h) PTH mRNA driven by a CMV promoter

Summary

Introduction

Parathyroid hormone (PTH) gene expression is regulated post-transcriptionally through the binding of the trans-acting proteins AU rich binding factor 1 (AUF1), Upstream of Nras (Unr) and KH-type splicing regulatory protein (KSRP) to an AU rich element (ARE) in PTH mRNA 3'-UTR. Serum calcium and phosphate concentrations, in turn, control PTH gene expression post-transcriptionally through regulated binding of the trans-acting proteins AU rich binding factor 1 (AUF1), Upstream of N-ras (Unr) and KH-type splicing regulatory protein (KSRP) to a type III AU rich element (ARE) in PTH mRNA 3'-UTR [1,2,3]. We have recently shown that the mRNA decay promoting protein KSRP decreases PTH mRNA stability and steady-state levels through the PTH mRNA ARE [3] Both KSRP and AUF1 bind to PTH mRNA in vitro and in intact parathyroid glands [3]. Calcium depletion increases the association of AUF1 with the PTH mRNA ARE and decreases KSRP binding to the ARE resulting in (page number not for citation purposes)

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