Structural and functional analysis of the insulin-like growth factor I receptor gene promoter

Haim Werner, Mark A. Bach, Bethel Stannard, Charles Roberts, Derek LeRoith

Research output: Contribution to journalArticle

94 Citations (Scopus)

Abstract

The insulin-like growth factor I receptor (IGF-I-R) gene is expressed in most body tissues. The levels of IGF-I-R mRNA, however, are regulated by a number of physiological conditions (development, differentiation, and hormonal milieu) as well as in certain pathological states (diabetes and tumors). To understand the molecular mechanisms which control the transcription of the IGF-I-R gene, we have cloned the promoter of the rat receptor gene and have characterized its activity by transient expression assays. Different fragments of the 5′-flanking region (subcloned upstream of a luciferase reporter gene) were transfected into buffalo rat liver 3A cells (a cell line with a low number of IGF-I binding sites) and Chinese hamster ovary cells (a cell line with a higher number of cell-surface receptors). In both cell lines, most of the promoter activity was located in the proximal 416 base pairs of 5′-flanking region. However, further dissection of this proximal fragment revealed a cell type-specific pattern of promoter activity. Thus, in buffalo rat liver 3A cells, subfragments of this region each contributed to total activity, suggesting that contiguous cis-elements can act together to activate transcription. In Chinese hamster ovary cells, on the other hand, subfragments of the proximal promoter region partially substituted for the proximal 416 base pairs of 5′-flanking region. Coexpression studies using an IGF-I-R promoter reporter construct together with an Sp1 expression vector (under the control of an ADH promoter) were performed in SL2 cells, a Drosophila cell line which lacks endogenous Sp1. The results obtained showed that Sp1 can trans-activate the IGF-I-R promoter in vivo. Transient transfection assays were complemented with gel-retardation assays and DNase I footprinting experiments, which showed that transcription factor Sp1 is potentially an important regulator of IGF-I-R gene expression.

Original languageEnglish (US)
Pages (from-to)1545-1558
Number of pages14
JournalMolecular Endocrinology
Volume6
Issue number10
StatePublished - 1992
Externally publishedYes

Fingerprint

IGF Type 1 Receptor
5' Flanking Region
Genes
Cell Line
Buffaloes
Cricetulus
Base Pairing
Ovary
Sp1 Transcription Factor
Liver
Deoxyribonuclease I
Cell Surface Receptors
Electrophoretic Mobility Shift Assay
Luciferases
Insulin-Like Growth Factor I
Reporter Genes
Genetic Promoter Regions
Drosophila
Transfection
Dissection

ASJC Scopus subject areas

  • Molecular Biology
  • Endocrinology, Diabetes and Metabolism

Cite this

Structural and functional analysis of the insulin-like growth factor I receptor gene promoter. / Werner, Haim; Bach, Mark A.; Stannard, Bethel; Roberts, Charles; LeRoith, Derek.

In: Molecular Endocrinology, Vol. 6, No. 10, 1992, p. 1545-1558.

Research output: Contribution to journalArticle

Werner, H, Bach, MA, Stannard, B, Roberts, C & LeRoith, D 1992, 'Structural and functional analysis of the insulin-like growth factor I receptor gene promoter', Molecular Endocrinology, vol. 6, no. 10, pp. 1545-1558.
Werner, Haim ; Bach, Mark A. ; Stannard, Bethel ; Roberts, Charles ; LeRoith, Derek. / Structural and functional analysis of the insulin-like growth factor I receptor gene promoter. In: Molecular Endocrinology. 1992 ; Vol. 6, No. 10. pp. 1545-1558.
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