Structure and Function of the Mouse Insulin-Like Growth Factor Binding Protein 5 Gene Promoter

Kou Kou, Donald W. Mittanck, Chong Fu, Peter Rotwein

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Abstract

The actions of insulin-like growth factors I and II (IGF-I and -II) are modulated by interactions with one or more of a family of secreted IGF binding proteins (IGFBPs). IGFBP-5, the most conserved of the six known IGFBPs, is a 252-amino-acid protein that has been shown both to potentiate and inhibit IGF action. In previous studies, we have cloned and characterized the mouse IGFBP-5 gene and demonstrated that it is expressed in a hierarchical pattern in different adult mouse tissues and during rodent embryonic development. In this report, we describe the initial analysis of the IGFBP-5 gene promoter. By transient gene transfer studies, we show the orientation-specific activity of DNA fragments containing from 31 to 4,100 bp from the 5'-flanking region of the mouse IGFBP-5 gene in directing expression of the heterologous reporter gene luciferase in Hep G2 cells. DNA fragments with only 156 bp of 5'-flanking sequence mediated over 60% of maximal promoter activity, and a segment containing the TATA box and the first 120 bp of exon 1 still conferred some promoter function. Within the highly active 156-bp region, we identified a 37-bp segment from −70 to −34 that exhibited specific binding in DNase I footprinting and gel-mobility shift experiments with Hep G2 nuclear protein extracts. The footprinted region, which is almost completely conserved in the rat and human IGFBP-5 genes, was responsible for at least 70% of the activity of the intact promoter, as evidenced by the deleterious consequences of small internal deletions within this sequence on promoter function. Taken together, our results demonstrate that the mouse IGFBP-5 gene promoter has a simple structure, and defines a framework for examining the mechanisms responsible for the multifactorial regulation of IGFBP-5 gene transcription during development and in the adult.

Original languageEnglish (US)
Pages (from-to)241-249
Number of pages9
JournalDNA and Cell Biology
Volume14
Issue number3
DOIs
StatePublished - Mar 1995

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ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cell Biology

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