IGF2BP3/IMP3 is identical to the K homology (KH)-domain-containing proteins overexpressed in cancer (KOC). In vivo, the protein encoded by this gene was found to bind to IGF2 leader 3 and leader 4 mRNAs and the H19 RNA. The binding of IMP3 to the 5′-untranslated region of the IGF2 leader 3 mRNA represses the translation of IGF2 during late development. The encoded protein contains several KH domains, which are important for RNA binding and are known to be involved in RNA synthesis and metabolism. A pseudogene is present on chromosome 7, and putative pseudogenes may exist on other chromosomes. The growth-regulating gene IMP3 has been characterized as a candidate for the Silver-Russell syndrome.