Insulin Like Growth Factor Binding Protein 5 (IGFBP5)

Insulin-like growth factor-binding protein 5 is a protein encoded by the IGFBP5 gene. Allander et al. (1994) showed that the IGFBP5 gene is divided into 4 exons and spans about 33 kb, primarily due to a first intron of approximately 25 kb. Primer extension studies identified the IGFBP5 mRNA cap site 772 bp 5-prime to the first nucleotide of the translation start codon. A potential TATA element beginning 33 bp 5-prime to the mRNA cap site was identified. When a DNA fragment containing this cap site and 461 bp of upstream sequence was placed 5-prime to the chloramphenicol acetyltransferase (CAT) reporter gene and transfected into human breast cancer cells, it directed CAT expression in an orientation-specific manner, suggesting that this region contains elements essential for IGFBP5 promoter activity.