A novel transcription unit within the exon sequence of the rat insulin like growth factor II gene

We identified a transcription unit within a single exon of the rat insulin like growth factor II (rIGFII) gene by a combination of Northern blotting, S1 nuclease mapping and primer extension analyses. Among multiple mRNA products of rIGFII, the 1.8kb transcript has a discrete 5' terminus and is encoded exclusively in a single 3'-extreme exon with no trace of the coding region. The upstream region of the 5' terminus contains a completely matching GC-rich 16bp palindrome and several sequence motifs highly homologous to the consensus sequences of binding sites for transcriptional regulatory proteins AP2, H2TF1 and NF-kappa B.