Heterogeneous Nuclear Ribonucleoprotein-A2/B1 Modulate Collagen Prolyl 4-Hydroxylase, α (I) mRNA Stability

Michael Fähling,Ralf Mrowka,Andreas Steege,Peter Martinka,Pontus B Persson,Bernd J Thiele

doi:10.1074/jbc.m510925200

Michael Fähling, Ralf Mrowka + Show 4 more

Open Access

https://doi.org/10.1074/jbc.m510925200

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Abstract

Collagen prolyl 4-hydroxylase (C-P4H) alpha-subunit is of regulatory importance in the assembling of C-P4H tetramers, which are necessary for the hydroxylation of procollagen chains. Change in collagen expression by hypoxia or iron diminishment is a significant issue in extracellular matrix remodeling. It was proposed that C-P4H-alpha (I) is regulated at the posttrancriptional level under these conditions. Here we report that the induction of C-P4H-alpha (I) in human fibrosarcoma cells HT1080 by the iron chelator 2,2-dipyridyl is predominantly caused by an enhancement of mRNA stability. This effect is mediated by an increased synthesis and binding of heterogeneous nuclear ribonucleoprotein (hnRNP)-A2/B1, which interacts with a (U)(16) element located in the 3'-untranslated region of C-P4H-alpha (I) mRNA. Luciferase reporter gene assays depending on C-P4H-alpha (I) 3'-untranslated region and co-transfection with hnRNP-A2/B1 provide evidence that the (U)(16) element is necessary and sufficient for posttranscriptional control of C-P4H-alpha (I) synthesis under the analyzed conditions. Further indication for the significance of hnRNP-A2/B1 in C-P4H-alpha (I) induction was obtained by micro array experiments. In a data set representing 686 independent physiological conditions, we found a significant positive correlation between hnRNP-A2/B1 and C-P4H-alpha (I) mRNAs.

Highlights

One of the most important factors in collagen synthesis is the collagen prolyl 4-hydroxylase, which is necessary for proline hydroxylation of procollagen chains
We present data that Collagen prolyl 4-hydroxylase (C-P4H)-␣ (I) mRNA is stabilized by interaction of RNA-binding proteins heterogeneous nuclear ribonucleoprotein (hnRNP)-A2/B1 with a U(16) element within the 3Ј-untranslated region (3Ј-UTR). mRNA stabilization by this phenomenon seems to be the key mechanism responsible for P4H induction under hypometabolic conditions caused by diminishment of Fe2ϩ ions by the iron chelator 2,2-dipyridyl
U(16) element. hnRNP-E1 shows no significant influence on C-P4H-␣ (I) 3Ј-UTR-dependent luciferase activity, independently of whether the U(16) element is present or not. n ϭ 8, **, p Ͻ 0.01

Summary

Introduction

One of the most important factors in collagen synthesis is the collagen prolyl 4-hydroxylase, which is necessary for proline hydroxylation of procollagen chains. We present data that C-P4H-␣ (I) mRNA is stabilized by interaction of RNA-binding proteins hnRNP-A2/B1 with a U(16) element within the 3Ј-UTR. Differences in luciferase activity depend only on posttranscriptional control, mediated by the UTRs, and involve mainly mRNA stability and translational efficiency.

Results

Conclusion