B. Guo et al., CHARACTERIZATION AND EXPRESSION OF IRON REGULATORY PROTEIN-2 (IRP2) -PRESENCE OF MULTIPLE IRP2, TRANSCRIPTS REGULATED BY INTRACELLULAR IRON LEVELS, The Journal of biological chemistry, 270(28), 1995, pp. 16529-16535
Iron regulatory proteins (IRP1 and IRP2) are RNA-binding proteins that
bind to stem-loop structures, termed iron-responsive elements (IREs),
present in either the 5'- or 3'-untranslated regions of specific mRNA
s. The binding of IRPs to 5'-IREs inhibits translation of mRNA, wherea
s the binding of IRPs to 3'-IREs stabilizes mRNA. To study the structu
re and regulation of IRP2, we isolated cDNAs for rat and human IRP2. T
he derived amino acid sequence of rat IPR2 is 93% identical with that
of human IRP2 and is present in lower eukaryotes, indicating that IRP2
is highly conserved, IRP1 and IRP2 share 61% overall amino acid ident
ity, IRP2 is ubiquitously expressed in rat tissues, the highest amount
s present in skeletal muscle and heart, IRP2 is encoded by multiple mR
NAs of 6.4, 4.0, and 3.7 kilobases, The 3'-untranslated region of rat
IRP2 contains multiple polyadenylation signals, two of which could acc
ount for the 4.0 kb and 3.7-kb mRNAs, The 3.7-kb mRNA is increased in
iron-depleted cells and occurs with a reciprocal decrease in the 6.4-k
b transcript, These data suggest that the 3.7-kb mRNA is produced by a
lternative poly(A) site utilization in iron-depleted cells.