Showing papers on "Iron response element published in 2009"

Remodeling of the pioneer translation initiation complex involves translation and the karyopherin importin β

Abstract: Mammalian mRNAs lose and acquire proteins throughout their life span while undergoing processing, transport, translation, and decay. How translation affects messenger RNA (mRNA)-protein interactions is largely unknown. The pioneer round of translation uses newly synthesized mRNA that is bound by cap-binding protein 80 (CBP80)-CBP20 (also known as the cap-binding complex [CBC]) at the cap, poly(A)-binding protein N1 (PABPN1) and PABPC1 at the poly(A) tail, and, provided biogenesis involves pre-mRNA splicing, exon junction complexes (EJCs) at exon-exon junctions. Subsequent rounds of translation engage mRNA that is bound by eukaryotic translation initiation factor 4E (eIF4E) at the cap and PABPC1 at the poly(A) tail, but that lacks detectable EJCs and PABPN1. Using the level of intracellular iron to regulate the translation of specific mRNAs, we show that translation promotes not only removal of EJC constituents, including the eIF4AIII anchor, but also replacement of PABPN1 by PABPC1. Remarkably, translation does not affect replacement of CBC by eIF4E. Instead, replacement of CBC by eIF4E is promoted by importin beta (IMPbeta): Inhibiting the binding of IMPbeta to the complex of CBC-IMPalpha at an mRNA cap using the IMPalpha IBB (IMPbeta-binding) domain or a RAN variant increases the amount of CBC-bound mRNA and decreases the amount of eIF4E-bound mRNA. Our studies uncover a previously unappreciated role for IMPbeta and a novel paradigm for how newly synthesized messenger ribonucleoproteins (mRNPs) are matured.

Expression and function of DMT1 without IRE in C6 cells mediated by recombinant adenovirus

Abstract: Divalent metal transporter 1 (DMT1) is a ferrous iron import protein. The improper expression of DMT1 is involved in neurodegenerative diseases. In the present study, we constructed a recombinant adenovirus containing the gene of DMT1 without the iron response element (DMT1-IRE) and investigated its expression and function in the C6 glioma cell line. The DMT1-IRE gene, obtained by RT-PCR, was cloned into the shuttle plasmiding pAdTrack-CMV containing green fluorescent protein (GFP) reporter gene. Linearized plasmid pAdTrack-CMV-DMT1-IRE was subsequently co-transformed into Escherichia coli (E. coli) BJ5183 cells along with an adenoviral backbone plasmid pAdEasy-1 after digestion with Pme I. Pac I-digested pAdEasy1-DMT1-IRE was then transfected into E1-transformed human embryonic kidney cells (HEK293 cells), in which recombinant adenoviruses were generated within 7 to 10 days. The results demonstrated that we obtained the DMT1-IRE gene. pAdEasy1-DMT1-IRE yielded a large fragment, plus a smaller fragment of 4.5 kb after digestion with Pac I. PCR confirmed pAdEasy1-DMT1-IRE contained gene DMT1-IRE, indicating the successful construction of recombinant adenovirus plasmid containing DMT1-IRE. GFP fluorescence further confirmed the generation of recombinant AdDMT1-IRE adenovirus. AdDMT1-IRE could efficiently infect C6 glioma cells. And cell viability decreased in AdDMT1-IRE infected cells after iron overload compared to the control. These results suggest that the over expressed DMT1-IRE can aggravate the iron induced cell death due to its iron influx function.