The inhibition of the iron responsive element RNA-protein interaction by heme does not mimic in vivo iron regulation.
Hemin at greater than 1 microM concentrations inhibits the interaction of the iron responsive element (IRE) and the iron responsive element binding protein (IRE-BP) as measured by gel retardation and UV cross-linking. Heme has recently been proposed to inhibit the repression of translation of an IRE-containing mRNA (Lin, J. J., Daniels-McQueen, S., Patino, M. M., Gaffield, L., Walden, W. E., and Thach, R. E., (1990) Science 247, 74-76). Our binding inhibition provides structural support for these observations. The action of hemin, however, does not mimic the physiologically demonstrated inhibition of high affinity binding of the IRE to IRE-BP by the oxidation of a sulfhydryl of the IRE-BP. In addition to this effect, hemin also inhibits a wide variety of RNA and DNA binding proteins, restriction endonucleases, and nucleases. Therefore, in vitro, the inhibitory effects of hemin are not limited to the interaction of the IRE-BP and the IRE, but are nonspecific and affect a wide variety of nucleic acid-protein interactions. Any hypothesis on the effects on protein-nucleic acid interactions employing greater than 1 microM concentrations of hemin should be interpreted with caution.
Haile
D J
DJ
Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892.
Rouault
T A
TA
Harford
J B
JB
Klausner
R D
RD
D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D003676:Deferoxamine / Q000494:pharmacology; D006418:Heme / Q000494:pharmacology*; D006801:Humans; D035925:Iron-Regulatory Proteins; D007700:Kinetics; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D011166:Porphyrins / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics*; D015183:Restriction Mapping; D012208:Rhabdomyosarcoma
D002352:Carrier Proteins; D035925:Iron-Regulatory Proteins; D015345:Oligonucleotide Probes; D011166:Porphyrins; D012333:RNA, Messenger; D006418:Heme; D003676:Deferoxamine