Cloning of the cDNA encoding an RNA regulatory protein--the human iron-responsive element-binding protein.
Iron-responsive elements (IREs) are stemloop structures found in the mRNAs encoding ferritin and the transferrin receptor. These elements participate in the iron-induced regulation of the translation of ferritin and the stability of the transferrin receptor mRNA. Regulation in both instances is mediated by binding of a cytosolic protein to the IREs. High-affinity binding is seen when cells are starved of iron and results in repression of ferritin translation and inhibition of transferrin receptor mRNA degradation. The IRE-binding protein (IRE-BP) has been identified as an approximately 90-kDa protein that has been purified by both affinity and conventional chromatography. In this report we use RNA affinity chromatography and two-dimensional gel electrophoresis to isolate the IRE-BP for protein sequencing. A degenerate oligonucleotide probe derived from a single peptide sequence was used to isolate a cDNA clone that encodes a protein containing 13 other sequenced peptides obtained from the IRE-BP. Consistent with previous characterization of the IRE-BP, the cDNA encodes a protein of 87 kDa with a slightly acidic pI, and the corresponding mRNA of approximately 3.6 kilobases is found in a variety of cell types. The encoded protein contains a nucleotide-binding consensus sequence and regions of cysteine and histidine clusters. This mRNA is encoded by a single gene on human chromosome 9, a finding consistent with previous localization by functional mapping. The protein contains no previously defined consensus motifs for either RNA or DNA binding. The simultaneous cloning of a different, but highly homologous, cDNA suggests that the IRE-BP is a member of a distinct gene family.
Rouault
T A
TA
Cell Biology and Metabolism Branch, National Institute of Child Health, Bethesda, MD 20892.
Tang
C K
CK
Kaptain
S
S
Burgess
W H
WH
Haile
D J
DJ
Samaniego
F
F
McBride
O W
OW
Harford
J B
JB
Klausner
R D
RD
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000302:isolation & purification; D002874:Chromosome Mapping; D002899:Chromosomes, Human, Pair 9; D003001:Cloning, Molecular; D006224:Cricetinae; D004247:DNA / Q000235:genetics* / Q000302:isolation & purification; D005293:Ferritins / Q000378:metabolism; D015723:Gene Library; D006801:Humans; D007501:Iron / Q000378:metabolism*; D033862:Iron-Binding Proteins; D035925:Iron-Regulatory Proteins; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics*; D011956:Receptors, Cell Surface / Q000235:genetics*; D011990:Receptors, Transferrin / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
D002352:Carrier Proteins; D033862:Iron-Binding Proteins; D035925:Iron-Regulatory Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D011990:Receptors, Transferrin; C027293:ferritin receptor; D004247:DNA; D005293:Ferritins; D007501:Iron