Contiguous localization of the genes encoding human insulin-like growth factor binding proteins 1 (IGBP1) and 3 (IGBP3) on chromosome 7.

In extracellular fluids the insulin-like growth factors (IGFs) are bound to specific binding proteins (IGBPs). The genes for two members of this protein family have been mapped, the IGBP1 gene to human chromosomal region 7p14-p12 and the IGBP2 gene to region 2q33-q34. In this study, somatic cell hybrid analysis indicated that IGBP3 is also located on chromosome 7. Pulsed-field gel electrophoresis was used to demonstrate the close physical linkage between IGBP1 and IGBP3. Overlapping cosmid clones encompassing these genes were isolated, and restriction endonuclease mapping showed that the genes are arranged in a tail-to-tail fashion separated by 20 kb of DNA. Further characterization of the IGBP1 DNA sequence disclosed a duplication of the intron 3-exon 4 junction within the third intron. In addition, we report RFLPs for ApaLI and TaqI in the IGBP1 locus.