Sa. Kohler et al., SUCCINATE-DEHYDROGENASE-B MESSENGER-RNA OF DROSOPHILA-MELANOGASTER HAS A FUNCTIONAL IRON-RESPONSIVE ELEMENT IN ITS 5'-UNTRANSLATED REGION, The Journal of biological chemistry, 270(51), 1995, pp. 30781-30786
Iron-responsive elements (IREs) are cis-acting mRNA stem-loop structur
es that specifically bind cytoplasmic iron regulatory proteins (IRPs),
IRP-IRE interactions mediate the coordinate post transcriptional regu
lation of key proteins in iron metabolism, such as ferritin, transferr
in receptor, and erythroid 5-aminolevulinic acid synthase. Depending o
n whether the IRE is located in the 5'- or 3'-untranslated region (UTR
), binding of IRP will inhibit mRNA translation or degradation, respec
tively, Here we describe a new IRE in the 5'-UTR of succinate dehydrog
enase subunit b (SDHb) mRNA of Drosophila melanogaster. The SDHb IRE b
inds in vitro to vertebrate and insect IRPs with a high affinity equal
to that of human ferritin H chain IRE. Under conditions of iron depri
vation, SDHb mRNA of Drosophila SL-2 cells shifts to a non-polysome-bo
und pool. Moreover, translation of a human growth hormone mRNA with th
e SDHb IRE in its 5'-UTR is iron-dependent in stably transfected L cel
ls, We conclude that the SDHb IRE mediates translational inhibition bo
th in insect and vertebrate cells, This constitutes the first identifi
cation of a functional IRE in insects. Furthermore, Drosophila SDHb re
presents the second example, after porcine mitochondrial aconitase, of
an enzyme of the citric acid cycle whose mRNA possesses all necessary
features for translational regulation by cellular iron levels.