Visit our Expo - Redox and Inflammation signaling 2012

Session XIV : Transcriptional and translational control Poster XIV, 39
Runx2 Transcription Factor Controls F promoter Activity of Human ER alpha Gene
in Osteoblasts
Elisabetta Lambertini, Elisa Tavanti, Letizia Penolazzi, Roberto Gambari and Roberta
Piva.
Department of Biochemistry and Molecular Biology, University of Ferrara, Italy. Email:
piv@unife.it
Bone growth, development and maintenance is a highly regulated process. The balance
between bone formation and resorption involves two cell types: bone forming osteoblasts
(OBs) and bone-resorbing osteoclasts (OCs). OBs-dependent bone formation varies with age,
metabolic disease states or with pharmacological intervention. OBs formation and maturation
are under control of a specific transcription factor, Runx2, that regulates the expression of
bone-specific genes. Another important transcription factor playing a central role in bone is
the estrogen receptor alpha (ER) that mediates estrogen-induced effects on gene expression.
Considering the potent gene regulatory activity of Runx2 and ER we investigated the role of
Runx2 on the regulation of ER expression valuating its interaction with F promoter of ER
gene. F promoter is one of the multiple promoters of human ER gene and is the only active
promoter in bone. In this promoter three Runx2 sites (A), (B), and (C) are present. To
understand if they are involved in influencing F promoter activity, different promoter-reporter
deletion and mutation constructs were assayed for function after transient transfection into the
Runx2-producing SaOS-2 human osteoblastic cells. The comparison of luciferase activities
allowed the identification of a negative role of a sequence context, within the F promoter
containing the three Runx2 binding sites. In addition, by using electrophoretic mobility shift
assay (EMSA) in combination with supershift we demonstrated that a significant supershifted
complex was formed only with the Runx2 (A) site. In order to demonstrate the
possible association of the Runx2 protein to the F promoter “ in vivo” chromatin
immunoprecipitation assay (ChIP) was performed. The results demonstrate that Runx2
interacts “ in vivo” with the region of the F promoter within the sequence context containing
the Runx2 binding sites in SaOS-2 cells indicating that Runx2 may be considered one of the
factors controlling specific expression of human ER alpha gene in osteoblasts.
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