In:
American Journal of Physiology-Lung Cellular and Molecular Physiology, American Physiological Society, Vol. 288, No. 6 ( 2005-06), p. L1089-L1098
Abstract:
Idiopathic pulmonary fibrosis (IPF) is an insidious lung disease with no known cure or effective therapy. Macrophage-derived insulin-like growth factor-I (IGF-I) is thought to play a role in the pathogenesis of IPF; however, little is known about the control of IGF-I expression in macrophages. In this report we investigated the cis-regulatory elements that control basal expression using luciferase reporter constructs in RAW 264.7 macrophages. We show that the +95 to +329 region contains elements necessary to direct maximal promoter activity, whereas the +251 to +329 region contains the minimal promoter. Mapping transcriptional start sites for endogenous IGF-I in primary macrophages revealed that the major transcriptional start site is centered at +150, whereas the most 3′-transcriptional start site is centered at +255. Nuclear proteins from primary and RAW 264.7 macrophages bind specifically to the region required for maximal promoter activity (+134 to +173) and to the region required for minimal promoter activity (+267 to +299). Antibody supershift assays indicate that Sp3 bound to the +267 to +299 region. Moreover, mutation of the putative binding site reduced Sp3 binding in EMSAs and increased promoter activity in luciferase reporter gene assays. We also found that the regions from −1711 to −855 and −855 to −337 contain putative macrophage-specific suppressor elements that do not function in HeLa or COS-7 epithelial cell lines. These data support the view that macrophage IGF-I expression is positively regulated by elements located in the 5′-untranslated region and negatively regulated by elements in the 5′-flanking region of the IGF-I gene.
Type of Medium:
Online Resource
ISSN:
1040-0605
,
1522-1504
DOI:
10.1152/ajplung.00352.2004
Language:
English
Publisher:
American Physiological Society
Publication Date:
2005
detail.hit.zdb_id:
1477300-4
SSG:
12
