Transcriptional activation of insulin-like growth factor binding protein 6 by 17beta-estradiol in SaOS-2 cells.
10.3858/emm.2009.41.7.053
- Author:
Yu yan ZHAO
1
;
Lei GUO
;
Xiao juan ZHAO
;
Hong LIU
;
Tian LEI
;
Dong Jie MA
;
Xiao Yu GAO
Author Information
1. Department of Endocrinology, First Affiliated Hospital, China Medical University, Shenyang 110001, China. g572@sina.com
- Publication Type:Original Article ; Research Support, Non-U.S. Gov't
- Keywords:
estrogen;
insulin-like growth factor binding protein 6;
osteoblasts;
receptors, estrogen;
transcription, genetic
- MeSH:
Blotting, Western;
Cell Proliferation;
Chloramphenicol O-Acetyltransferase/metabolism;
Electrophoretic Mobility Shift Assay;
Estradiol/*pharmacology;
Estrogen Receptor alpha/genetics/metabolism;
Estrogens/pharmacology;
Humans;
Insulin-Like Growth Factor Binding Protein 6/*genetics/metabolism;
Osteoblasts/*drug effects/metabolism;
Promoter Regions, Genetic/*genetics;
RNA, Messenger/genetics/metabolism;
Response Elements;
Reverse Transcriptase Polymerase Chain Reaction;
*Transcriptional Activation;
Tumor Cells, Cultured
- From:Experimental & Molecular Medicine
2009;41(7):478-486
- CountryRepublic of Korea
- Language:English
-
Abstract:
Osteoblasts can synthesize the insulin-like growth factors (IGFs) and the IGF-binding proteins (IGFBPs), which may either enhance or attenuate IGF-stimulated bone cell proliferation. Since estrogen induced osteoblastic differentiation and proliferation through an estrogen-responsive gene in target cells, we investigated the effects of estrogen on IGFBP-6 expression in the human osteoblastic-like cell line SaOS-2. Expressions of IGFBP-6 protein and mRNA increased 2.8 and 2-fold, respectively, in the presence of 17-beta-estradiol (E2) (0.01 to 1 micrometer) and estrogen receptor (ER) in SaOS-2 cells. On the other hand, E2 induced a 2-fold increase in SaOS-2 cell proliferation. To identify genomic sequences associated with estrogen responsiveness, the 5'-promoter region (-44 to +118) of the IGFBP-6 gene was cloned into a chloramphenicol acetyltransferase (CAT) reporter vector. E2 induced a 3-fold increase in CAT activity in SaOS-2 cells transiently transfected with this construct. Identification of the estrogen-responsive element (ERE) [5'-CCTTCA CCTG-3'] (-9 to +1) in this IGFBP-6 gene promoter region was confirmed using electromobility shift assays and deletion analysis. This functional ERE was important for E2-induced trans-activation of the IGFBP-6 gene. These results demonstrate that E2 exhibits a positive effect on IGFBP-6 gene transcription through estrogen-liganded ER binding to the functional ERE in the IGFBP-6 gene promoter in SaOS-2 cells.
