Key points are not available for this paper at this time.
Iron regulatory proteins (IRPs) 1 and 2 bind with equally high affinity to iron-responsive element (IRE) RNA stem-loops located in mRNA untranslated regions and, thereby, post-transcriptionally regulate several genes of iron metabolism. In this study we define the RNA-binding specificities of mouse IRP-1 and IRP-2. By screening loop mutations of the ferritin H-chain IRE, we show that both IRPs bind well to a large number of IRE-like sequences. More significantly, each IRP was found to recognize a unique subset of IRE-like targets. These IRP-specific groups of IREs are distinct from one another and are characterized by changes in certain paired (IRP-1) or unpaired (IRP-2) loop nucleotides. We further demonstrate the application of such sequences as unique probes to detect and distinguish IRP-1 from IRP-2 in human cells, and observe that the IRPs are regulated similarly by iron and reducing agents in human and rodent cells. Importantly, the ability of each IRP to recognize an exclusive subset of IREs was conserved between species. These findings suggest that IRP-1 and IRP-2 may each regulate unique mRNA targets in vivo, possibly extending their function beyond the regulation of intracellular iron homeostasis. Iron regulatory proteins (IRPs) 1 and 2 bind with equally high affinity to iron-responsive element (IRE) RNA stem-loops located in mRNA untranslated regions and, thereby, post-transcriptionally regulate several genes of iron metabolism. In this study we define the RNA-binding specificities of mouse IRP-1 and IRP-2. By screening loop mutations of the ferritin H-chain IRE, we show that both IRPs bind well to a large number of IRE-like sequences. More significantly, each IRP was found to recognize a unique subset of IRE-like targets. These IRP-specific groups of IREs are distinct from one another and are characterized by changes in certain paired (IRP-1) or unpaired (IRP-2) loop nucleotides. We further demonstrate the application of such sequences as unique probes to detect and distinguish IRP-1 from IRP-2 in human cells, and observe that the IRPs are regulated similarly by iron and reducing agents in human and rodent cells. Importantly, the ability of each IRP to recognize an exclusive subset of IREs was conserved between species. These findings suggest that IRP-1 and IRP-2 may each regulate unique mRNA targets in vivo, possibly extending their function beyond the regulation of intracellular iron homeostasis. INTRODUCTIONThe regulation of cellular iron homeostasis is under the post-transcriptional control of iron regulatory protein-1 (IRP-1), ( 1The abbreviations used are: IRPiron regulatory proteinIREiron-responsive element2-ME2-mercaptoethanolUTRuntranslated region.) a cytoplasmic RNA-binding protein with specificity for mRNA stem-loop structures known as iron-responsive elements (IREs) (reviewed by Klausner et al. (33.Klausner R.D. Rouault T.A. Harford J.B. Cell. 1993; 72: 19-26Abstract Full Text PDF PubMed Scopus (1046) Google Scholar) and Kühn(35.Kühn L.C. Hershko C. Bailliere's Clinical Haematology. 7. Bailliere Tindall, London1994: 763-785Google Scholar)). IRP-1, formerly referred to as IRE-binding protein (Rouault et al., 46.Rouault T.A. Hentze M.W. Caughman S.W. Harford J.B. Klausner R.D. Science. 1988; 241: 1207-1210Crossref PubMed Scopus (239) Google Scholar; Leibold and Munro, 36.Leibold E.A. Munro H.N. Proc. Natl. Acad. Sci. U. S. A. 1988; 85: 2171-2175Crossref PubMed Scopus (554) Google Scholar), iron regulatory factor (IRF; Müllner et al., 1989), or ferritin repressor protein (Walden et al., 55.Walden W.E. Daniels-McQueen S. Brown P.H. Gaffield L. Russell D.A. Bielser D. Bailey L.C. Thach R.E. Proc. Natl. Acad. Sci. U. S. A. 1988; 85: 9503-9507Crossref PubMed Scopus (81) Google Scholar), has been identified as the cytosolic counterpart of the citric acid cycle enzyme, aconitase (Hentze and Argos, 27.Hentze M.W. Argos P. Nucleic Acids Res. 1991; 19: 1739-1740Crossref PubMed Scopus (127) Google Scholar; Rouault et al., 47.Rouault T.A. Stout C.D. Kaptain S. Harford J.B. Klausner R.D. Cell. 1991; 64: 881-883Abstract Full Text PDF PubMed Scopus (229) Google Scholar; Kaptain et al., 30.Kaptain S. Downey W.E. Tang C. Philpott C. Haile D. Orloff D.G. Harford J.B. Rouault T.A. Klausner R.D. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 10109-10113Crossref PubMed Scopus (157) Google Scholar; Haile et al., 22.Haile D.J. Rouault T.A. Tang C.K. Chin J. Harford J.B. Klausner R.D. Proc. Natl. Acad. Sci. U. S. A. 1992; 89: 7536-7540Crossref PubMed Scopus (214) Google Scholar; Kennedy et al., 31.Kennedy M.C. Mende-Mueller L. Blondin G.A. Beinert H. Proc. Natl. Acad. Sci. U. S. A. 1992; 89: 11730-11734Crossref PubMed Scopus (296) Google IRP-1 is as a of between RNA and cellular iron et al., D.J. Rouault T.A. Harford J.B. Kennedy M.C. Blondin G.A. Beinert H. Klausner R.D. Proc. Natl. Acad. Sci. U. S. A. 1992; 89: PubMed Scopus Google Scholar; et al., A. S. Hentze M.W. Proc. Natl. Acad. Sci. U. S. A. 1992; 89: PubMed Scopus Google Scholar; et al., A. H. L. L.C. Nucleic Acids Res. 1993; PubMed Scopus Google Scholar; et al., Kennedy M.C. Beinert H. Klausner R.D. Rouault T.A. PubMed Scopus Google In cells, IRP-1 of ferritin and acid by to IREs located in their and Munro, Munro H.N. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar; Hentze et al., M.W. Caughman S.W. Rouault T.A. A. Harford J.B. Klausner R.D. Science. PubMed Scopus Google Scholar; et al., A. L. J. 1993; Full Text PDF PubMed Google Scholar; et al., Hentze M.W. J. 1993; Full Text PDF PubMed Google of IRP-1 to a of IREs in the of mRNA this et al., Hentze M.W. Caughman S.W. Rouault T.A. Klausner R.D. Harford J.B. Science. 1988; PubMed Scopus Google Scholar; Müllner and L.C. Cell. 1988; Full Text PDF PubMed Scopus Google Scholar; Müllner et al., L.C. Cell. Full Text PDF PubMed Scopus Google Scholar; et al., Klausner R.D. Harford J.B. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google of this is cellular iron and iron is as IRP-1 well to the (reviewed by IRE-binding protein has been characterized in et al., C. L.C. J. 1993; Full Text PDF PubMed Google Scholar; et al., Leibold E.A. J. Full Text PDF PubMed Google Scholar) and in human et al., Chin J. Rouault Klausner R.D. J. Full Text PDF PubMed Google Scholar), and is referred to as IRP-2. IRP-2 is a protein that to known mRNA IREs with an affinity equally as high as that of IRP-1 et al., 1993; et al., proteins are by genes (Rouault et al., and their sequences (Rouault et al., T.A. Haile D.J. Downey W.E. Philpott Tang C. Chin J. Orloff D. Harford J.B. Klausner R.D. 1992; PubMed Scopus Google Scholar; et al., Brown Leibold E.A. J. Full Text Full Text PDF PubMed Scopus Google Scholar) of known to a in IRP-1 et al., Haile D. Rouault T.A. Klausner R.D. J. 1993; Full Text PDF PubMed Google Scholar; et al., H. L.C. J. PubMed Scopus Google Scholar), IRP-2 is et al., IRPs both to IRP-1 is between and RNA-binding (reviewed by is iron of IRP-2 protein and et al., Hentze M.W. Google Scholar), and by iron of IRP-2 protein et al., et al., by a and IRPs are to the of in et al., et al., Klausner R.D. Rouault T.A. J. Full Text Full Text PDF PubMed Scopus Google Scholar), and both proteins are mRNA in that the IRPs may bind IRE-like and regulate an of is by a study in a of IRP-1 sequences from a of ferritin et al., C. L.C. J. Full Text PDF PubMed Google several of to IRP-1 and to IRP-2. These findings suggest that the RNA-binding specificities of proteins are We that IRP-2 bind to to a unique of RNA targets. In this study we this the ferritin as a for as this is the IRP and a of well characterized is for et al., By of loop we define and the RNA-binding specificities of mouse IRP-1 and IRP-2. findings demonstrate the that a loop has RNA by both IRPs and a of that bind to IRP-2. an is for the of human IRP-1 from IRP-specific RNA we show that several that distinguish the regulation of rodent IRP-1 and IRP-2 are well conserved in and and human and in cells, and in human and in with for and of intracellular iron was by of with from iron was to with for with in to IRE-binding and the in and 1 cytoplasmic protein was to in in a of was a to a in A. was in and and proteins from the in a of to was to 1 to each and was by for was for IRP-1 and IRP-2 each with IRP-1 or IRP-2 by a ferritin from a et al. of the was by and that with human IRP-1 or both IRP-1 and IRP-2 et by of IREs of a to the ferritin for of the conserved in the loop and of et of was in the 1 a loop the for the with the loop 2 from of 1 in that the loop was to with that of loop and of is in and used to In each protein was in and the of IRP was by the number of sequences in each RNA of was and RNA probes used to high to detect a protein to a with high certain IRP-1 or RNA of as by of to the 2 RNA and by a and extending with with and and as in of each for to mouse IRP-1 or IRP-2. was from of and used as for in of RNA of each was with of cytoplasmic and by sequences identified by and by the of et S. A. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar) the and S. of sequences. to the 2 and RNA and IRP-1 or IRP-2 sequences identified by the of with and for to IRP-1 or IRP-2 by IRPs in in or human ferritin is as a is a by et to of the with to RNA In was with RNA in a and and of for or for and from as et al., by for with cytoplasmic IRP or human IRP-1 as proteins with et al., H. J. P. L.C. J. 1993; PubMed Scopus Google Scholar) or a et al., S. A. H. L.C. Hentze M.W. J. 1993; PubMed Scopus Google Scholar), and as et al., the in the of to and with to IRPs in to detect human IRPs IRP-specific Importantly, human IRP-2 to rodent and and for to in the of to of human cytoplasmic was with of and with of or for in the or of of human IRP-2 and in the of and a with of RNA-binding for of a ferritin to IRP-1 is between and et al., D.J. Hentze M.W. Rouault T.A. Harford J.B. Klausner R.D. Cell. PubMed Google Scholar; et al., A. Munro H.N. J. Full Text PDF PubMed Google for the for sequences that bind to the IRPs and are to we to was a to the of each the of to IRP of a by et C. S. J. A. J. PubMed Scopus Google Scholar)). was with a of RNA to for in the of and by IRP in the used was by to bind a for each and the of the of and sequences the of each RNA by et al. to in the of each RNA was and and for to IRP-1 or IRP-2 in by of by each of was to the IRE, and a to each of 2 of was with an of cytoplasmic in the of for specificity of the was by the of of and of a stem-loop RNA et al., was by of of for was to for and 2 a for by an with 1 of in and a of to of this study was to define and the RNA-binding specificities of IRP-1 and IRP-2. the cellular of each IRP et al., J. 1993; Full Text PDF PubMed Google Scholar; and L.C. J. Full Text Full Text PDF PubMed Scopus Google Scholar), we with a to for IRE-binding proteins a and for sequences. from mouse with for to IRP was a and proteins by from to IRP-1 and IRP-2 identified by RNA and their specificity by and RNA a between IRP RNA and protein and IRP-1 was in the as et al., et al., a was with of IRP-1 may to in RNA-binding specificity to the of IRP-1 and of IRP-2 with IRP-2 in a RNA-binding protein with the ferritin this protein equally as well to RNA stem-loops of and was of IRE-binding proteins in mouse cytoplasmic was by a and 1 of by with of IRE, and to IRP-1 and IRP-2 are IRE-binding protein was in this RNA-binding protein was for was with a and is in the the of as each was 1 IRP-1 in the of IRP was of IRP-2 in the and in the IRP-2 IRP-1 of the identified IRP-1 and IRP-2 as the IRE-binding proteins in cells. proteins may that bind RNA of to the IRE, we with a ferritin the conserved loop and et and and several In to the specificity of the a of RNA in the and the loop 1 RNA in of the mouse of IRP-1 and IRP-2 to certain and probes in and a of we identified proteins with specificity for IRE-like sequences. We to suggest the of by IRP-1 and IRP-2 a we of IRP-1 to IREs or between 1 and to IREs et al., the IREs as to rodent IRP-1 and in to IRP-2 et al., we the IRP for paired RNA of of IRE-like was the 1 2 RNA from the in that the of the loop was to with the of certain IRE-like RNA by to in of paired RNA probes the of IRP-1 for and and in of IRP-1 to IREs was as IRP-1 well to et al., by IRP-2 a for loop IRP-2 recognize and IRP to IREs with an loop in of IRP-1 and IRP-2 that the loop and for protein et These may in the specificity of IRP-1 and IRP-2. this we to the and probes in and from each for to IRP-1 or IRP-2 in and the of in by and as et and and We identified and and for to mouse IRP-1 and IRP-2 to a ferritin loop is loop both IRP-1 and IRP-2 as well as the of to ferritin for sequences are in and are with affinity from a in the of each the in the of and a the in the of and et and of loop of is to the of 1 and are in large and are of each RNA by or by each RNA and IRP of each with a for an the and for and are to the IRE, a of in the of is a of RNA of the sequences and been a et al., and affinity sequences from each well to both IRP-1 and we with for mouse By we identified to IRP-2 to to of the a loop from the 2 and of the loop in their of and loop is in this as by to both IRPs and 1The the specificity for as by of and We further the specificity of this by of the to mouse IRP-1 and IRP-2 was to a IRE, in the or of in the of the mouse IRP-2 as well as the IRE, to IRP-1 the of the by of the to IRP-2 as to of as an RNA of an RNA RNA was to for to mouse IRP-1 or IRP-2. of each was with IRP in the or of of was by and the to of of for IRP-1 and of RNA sequences by mouse IRP-1 and IRP-2 are are of in human cells. is to distinguish the RNA of human IRP-1 and as the human et al., We RNA probes for mouse IRP-1 or IRP-2 show for the human In to of the such probes a to distinguish IRP-1 from IRP-2 in human this we characterized one to mouse IRP-2 this and a et IREs bind to rodent IRP-1 or IRP-2 with and that of a in the of and et the ability of each IRP-specific to bind of human IRP-1 to of IRP-1 protein as as the of of the to a protein as by with RNA stem-loops the in affinity of probes for human We the ability of and to with mouse and human cytoplasmic of to proteins of and probes to mouse IRP-1 IRP-2 proteins from mouse was under to distinguish between the human are of Rouault et of human of probes to a We the affinity of the for human IRP-1, that the human protein by this is of probes for human IRP-1 and IRP-2. of and probes for to of human IRP-1 by probes with of a protein or and to IRE, is the probes to proteins in mouse IRP-1 or IRP-2 and in human cytoplasmic and a probes to proteins to mouse IRP-1 IRP-2 as to a protein in human in to proteins that may IRP of to the and IRP-1 from IRP-2 in from human in with to IRP RNA and by RNA probes of human was to that of mouse IRP-1 and as a in the both mouse IRP the and probes the by and the of and to the to for in RNA-binding of IRP-1 and IRP-2 RNA in human cells. cytoplasmic from human was with and IRP-specific in the of and and by 2 of mouse was as a probes human the as mouse IRP-2 IRP-1 and probes to in of the human IRPs of was for and to for in of the was to the of probes for the mouse as by of the mouse IRP and the as the for IRP-1 and IRP-2 probes the the IRP-2 is the a human with a to that of the ferritin IRP-1 was in human and cells. By the a the as that of IRP-1 in human the was IRP-2 was in and in and was a loop the was that the exclusive specificities of IRP-1 and IRP-2 are conserved between and the IRP-specific probes a for the of the human and that their is of IRP-1 and IRP-2 by Iron and the of IRP-1 and IRP-2 is iron regulated in human cells. in IRP-1 was by of and by the of iron for in and cells, in cells. IRP-1 in with IRP-2 in the as IRP-1 to changes in iron by in from is in with the between IRP-1 and IRP-2 in rodent et al., suggest that iron IRP-2 protein in and cells, is by of IRP-2 protein in et al., Leibold E.A. J. Full Text Full Text PDF PubMed Scopus Google IRP-2 was in and in cells. IRP-2 that of IRP-1, was to iron in regulation of human IRP-1 and IRP-2. was from and cells, in or for with or of by and of with of with iron was 2 of each was with of and RNA probes in the of and the or of and by for or and the in the to for in was with that human IRP-1 and IRP-2 are In we that of with the of IRP-2 by the of IRP-1 for was with the and with rodent IRP-2 and findings suggest that probes detect and between the human the that distinguish of IRP-1 from IRP-2 are well conserved between human and rodent a unique cellular the post-transcriptional regulation of several the that IRP-1 and IRP-2 each function as mRNA in intracellular iron as both proteins are regulated by iron et al., mRNA in et al. et al., and bind ferritin and mRNA IREs with equally high affinity et al., 1993; et al., In this we further show that the IRPs conserved the ability to recognize exclusive and distinct of the that the IRPs may regulate mRNA targets. We of the that by or both IRPs and used this to an for the of IRP RNA in human in RNA-binding screening was to define the RNA-binding specificities of mouse IRP-1 and IRP-2 that IRE-binding by both IRPs a between 1 and of the was as a of RNA-binding by IRP-1 et al., that by IRP-2 a loop may in the RNA-binding of the of loop IRP and, in the of loop was by IRP In the we identified and as the ferritin loop by both was of changes was of in the and loop IRP-1 a and et al., of the or for IRP-1, we identified such sequences that to IRP-2. a of loop 2 and to unpaired and for protein These findings are to the ferritin IRE, as of an loop to the acid in for the affinity was We the loop and identified changes in paired or unpaired that are by IRP-1 or IRP-2. These findings that the IRPs bind of RNA of regulatory RNA-binding proteins is and several of bind with specificity to RNA structures (reviewed in and A. Scholar), and Science. PubMed Scopus Google Scholar), and and H. Sci. Full Text PDF PubMed Scopus Google Scholar)). from the IRPs and are of proteins known to between RNA targets in loop proteins and are one and bind RNA stem-loops (reviewed by and Scholar)). the and proteins are in and as that recognize RNA in the loop et J. Full Text PDF PubMed Google Scholar)). of the RNA loop sequences by and proteins was to a acid et al., the of IRP-1 and IRP-2 (Rouault et al., may for their to bind a IRE, equally as to the acid the specificities of the a the such that the and for are for with IRP-1 and IRP-2 by et We that the unpaired loop to with IRP as was for that between the and and their and et al., T.A. 1991; PubMed Scopus Google Scholar; et al., J. D. 1993; PubMed Scopus Google Scholar), and for the RNA stem-loop and protein et al., C. PubMed Scopus Google in by the IRPs loop 2 and is by IRP-2. is that IRP-1 is of in the IRP-1 is to the a the loop with to the ability of IRP-1, to bind IRE-like with in 1993; Scopus (81) Google Scholar; et al., RNA with and to the possibly in and by IRP-2. the loop may a in et al., H. Nucleic Acids Res. PubMed Scopus Google Scholar), and to loop to RNA with the of the are to Iron of IRP-1 and IRP-2 in and application was found for the RNA used as probes to distinguish human IRP-1 from IRP-2. the rodent human IRP-1 and IRP-2 are of and their RNA by has of human IRP as a that human a of the to detect human IRP-2 human et al., or to human with et al., this we that IRE-like for mouse IRP-1 or IRP-2 for the human an in by a affinity of the the of and sequences a for human IRP-2 of human IRP and as in rodent and IRP-1 was In the human IRPs of the that distinguish rodent IRP-1 and IRP-2. of the human proteins regulated by IRP-1 was in from by in with We that of mouse IRP-1, was and in the iron regulatory of the IRPs in human cells. These findings several of IRP regulation that are well conserved and a to detect human IRP RNA in IRP and and IRP-2 are proteins that several each bind to IREs conserved in known J. PubMed Scopus Google Scholar), their RNA are by iron et al., 1993; this and of in et al., et al., has between the iron both IRP-2 is et al., et al., and by a and that IRP-2 are by another IRP-2 to certain and in IRP-2 and A. J. Full Text PDF PubMed Google Scholar), in et al., L. A. A. J. Full Text Full Text PDF Scopus Google These in IRP or protein regulation may in the of of IRP mRNA et al., protein et al., and RNA et al., in this study further that the IRPs function cellular or of findings to this by that each IRP has a distinct RNA-binding is conserved between species. that each IRP may regulate distinct of mRNA targets in We are the acid to such mRNA in the that this further the function of and iron with cellular INTRODUCTIONThe regulation of cellular iron homeostasis is under the post-transcriptional control of iron regulatory protein-1 (IRP-1), ( 1The abbreviations used are: IRPiron regulatory proteinIREiron-responsive element2-ME2-mercaptoethanolUTRuntranslated region.) a cytoplasmic RNA-binding protein with specificity for mRNA stem-loop structures known as iron-responsive elements (IREs) (reviewed by Klausner et al. (33.Klausner R.D. Rouault T.A. Harford J.B. Cell. 1993; 72: 19-26Abstract Full Text PDF PubMed Scopus (1046) Google Scholar) and Kühn(35.Kühn L.C. Hershko C. Bailliere's Clinical Haematology. 7. Bailliere Tindall, London1994: 763-785Google Scholar)). IRP-1, formerly referred to as IRE-binding protein (Rouault et al., 46.Rouault T.A. Hentze M.W. Caughman S.W. Harford J.B. Klausner R.D. Science. 1988; 241: 1207-1210Crossref PubMed Scopus (239) Google Scholar; Leibold and Munro, 36.Leibold E.A. Munro H.N. Proc. Natl. Acad. Sci. U. S. A. 1988; 85: 2171-2175Crossref PubMed Scopus (554) Google Scholar), iron regulatory factor (IRF; Müllner et al., 1989), or ferritin repressor protein (Walden et al., 55.Walden W.E. Daniels-McQueen S. Brown P.H. Gaffield L. Russell D.A. Bielser D. Bailey L.C. Thach R.E. Proc. Natl. Acad. Sci. U. S. A. 1988; 85: 9503-9507Crossref PubMed Scopus (81) Google Scholar), has been identified as the cytosolic counterpart of the citric acid cycle enzyme, aconitase (Hentze and Argos, 27.Hentze M.W. Argos P. Nucleic Acids Res. 1991; 19: 1739-1740Crossref PubMed Scopus (127) Google Scholar; Rouault et al., 47.Rouault T.A. Stout C.D. Kaptain S. Harford J.B. Klausner R.D. Cell. 1991; 64: 881-883Abstract Full Text PDF PubMed Scopus (229) Google Scholar; Kaptain et al., 30.Kaptain S. Downey W.E. Tang C. Philpott C. Haile D. Orloff D.G. Harford J.B. Rouault T.A. Klausner R.D. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 10109-10113Crossref PubMed Scopus (157) Google Scholar; Haile et al., 22.Haile D.J. Rouault T.A. Tang C.K. Chin J. Harford J.B. Klausner R.D. Proc. Natl. Acad. Sci. U. S. A. 1992; 89: 7536-7540Crossref PubMed Scopus (214) Google Scholar; Kennedy et al., 31.Kennedy M.C. Mende-Mueller L. Blondin G.A. Beinert H. Proc. Natl. Acad. Sci. U. S. A. 1992; 89: 11730-11734Crossref PubMed Scopus (296) Google IRP-1 is as a of between RNA and cellular iron et al., D.J. Rouault T.A. Harford J.B. Kennedy M.C. Blondin G.A. Beinert H. Klausner R.D. Proc. Natl. Acad. Sci. U. S. A. 1992; 89: PubMed Scopus Google Scholar; et al., A. S. Hentze M.W. Proc. Natl. Acad. Sci. U. S. A. 1992; 89: PubMed Scopus Google Scholar; et al., A. H. L. L.C. Nucleic Acids Res. 1993; PubMed Scopus Google Scholar; et al., Kennedy M.C. Beinert H. Klausner R.D. Rouault T.A. PubMed Scopus Google In cells, IRP-1 of ferritin and acid by to IREs located in their and Munro, Munro H.N. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar; Hentze et al., M.W. Caughman S.W. Rouault T.A. A. Harford J.B. Klausner R.D. Science. PubMed Scopus Google Scholar; et al., A. L. J. 1993; Full Text PDF PubMed Google Scholar; et al., Hentze M.W. J. 1993; Full Text PDF PubMed Google of IRP-1 to a of IREs in the of mRNA this et al., Hentze M.W. Caughman S.W. Rouault T.A. Klausner R.D. Harford J.B. Science. 1988; PubMed Scopus Google Scholar; Müllner and L.C. Cell. 1988; Full Text PDF PubMed Scopus Google Scholar; Müllner et al., L.C. Cell. Full Text PDF PubMed Scopus Google Scholar; et al., Klausner R.D. Harford J.B. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google of this is cellular iron and iron is as IRP-1 well to the (reviewed by IRE-binding protein has been characterized in et al., C. L.C. J. 1993; Full Text PDF PubMed Google Scholar; et al., Leibold E.A. J. Full Text PDF PubMed Google Scholar) and in human et al., Chin J. Rouault Klausner R.D. J. Full Text PDF PubMed Google Scholar), and is referred to as IRP-2. IRP-2 is a protein that to known mRNA IREs with an affinity equally as high as that of IRP-1 et al., 1993; et al., proteins are by genes (Rouault et al., and their sequences (Rouault et al., T.A. Haile D.J. Downey W.E. Philpott Tang C. Chin J. Orloff D. Harford J.B. Klausner R.D. 1992; PubMed Scopus Google Scholar; et al., Brown Leibold E.A. J. Full Text Full Text PDF PubMed Scopus Google Scholar) of known to a in IRP-1 et al., Haile D. Rouault T.A. Klausner R.D. J. 1993; Full Text PDF PubMed Google Scholar; et al., H. L.C. J. PubMed Scopus Google Scholar), IRP-2 is et al., IRPs both to IRP-1 is between and RNA-binding (reviewed by is iron of IRP-2 protein and et al., Hentze M.W. Google Scholar), and by iron of IRP-2 protein et al., et al., by a and IRPs are to the of in et al., et al., Klausner R.D. Rouault T.A. J. Full Text Full Text PDF PubMed Scopus Google Scholar), and both proteins are mRNA in that the IRPs may bind IRE-like and regulate an of is by a study in a of IRP-1 sequences from a of ferritin et al., C. L.C. J. Full Text PDF PubMed Google several of to IRP-1 and to IRP-2. These findings suggest that the RNA-binding specificities of proteins are We that IRP-2 bind to to a unique of RNA targets. In this study we this the ferritin as a for as this is the IRP and a of well characterized is for et al., By of loop we define and the RNA-binding specificities of mouse IRP-1 and IRP-2. findings demonstrate the that a loop has RNA by both IRPs and a of that bind to IRP-2. an is for the of human IRP-1 from IRP-specific RNA we show that several that distinguish the regulation of rodent IRP-1 and IRP-2 are well conserved in
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