Control of insulin-like growth factor-II/mannose 6-phosphate receptor gene transcription by proximal promoter elements

Molecular Endocrinology
Z LiuP Rotwein

Abstract

The insulin-like growth factor-II/cation-independent mannose 6-phosphate receptor (IGF-II/MPR) is a multifunctional protein that binds IGF-II and ligands containing a mannose 6-phosphate recognition marker. Recent studies have shown that this receptor plays a critical role in mammalian development, and that its expression is controlled by both epigenetic and tissue-specific factors. Our laboratory has cloned the 93-kilobase mouse gene and characterized its 48 exons. In this report we describe the structure and function of the IGF-II/MPR gene promoter. To study promoter function, a series of chimeric plasmids linking different segments of IGF-II/MPR 5' flanking DNA to the reporter gene, firefly luciferase, were transiently transfected into HepG2 and C3H 10T1/2 cells. Promoter activity was orientation-specific and was maximal (550- to 4250-fold above promoterless control) with a plasmid containing 266 base pairs (bp) of IGF-II/MPR DNA. The fusion gene accurately directed transcription as measured by ribonuclease protection assay using RNA extracted from transfected cells. DNA-protein binding studies by in vitro DNase I footprinting revealed an extended 54-bp footprint within the proximal promoter that contained two E-boxes and po...Continue Reading

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