Poly(rC)-binding proteins (PCBPs) are cellular RNA-binding proteins; these proteins are defined by their triple KH structure and poly(C)-binding specificity. The 3 KH domains are not only involved in nucleic acid binding but also in mediating protein-protein interactions within the RNP complexes. PCBPs bind specifically to polypyrimidine tracts within the 3′ UTR of target mRNAs through the KH domains. PCBPs are expressed as 4 isoforms in cells. PCBP1 and PCBP2 are widely expressed in both the nucleus and the cytoplasm and can shuttle from the nucleus to the cytoplasm, while PCBP3 and PCBP4 are expressed to a less extent. PCBP1 and PCBP2 have been reported to stabilize the target mRNAs such as those of -globin, 1(I) collagen, and tyrosine hydroxylase by binding to C-rich 3′ UTR motifs. The 15-lipoxygenase mRNA is translationally silent until reticulocytes in the peripheral blood undergo the final steps of maturation. This translational silencing has been shown to be mediated by the binding of PCBP1 and hnRNPK to the 3′ UTR of 15-lipoxygenase mRNA.