Affordable Access

deepdyve-link
Publisher Website

Control of Fiat (factor inhibiting ATF4-mediated transcription) expression by Sp family transcription factors in osteoblasts.

Authors
  • Hekmatnejad, Bahareh1
  • Gauthier, Claude
  • St-Arnaud, René
  • 1 Genetics Unit, Shriners Hospitals for Children-Canada, Montreal, Quebec, Canada H3G 1A6. , (Canada)
Type
Published Article
Journal
Journal of Cellular Biochemistry
Publisher
Wiley (John Wiley & Sons)
Publication Date
Aug 01, 2013
Volume
114
Issue
8
Pages
1863–1870
Identifiers
DOI: 10.1002/jcb.24528
PMID: 23463631
Source
Medline
License
Unknown

Abstract

FIAT (factor inhibiting ATF4-mediated transcription) represses Osteocalcin gene transcription and inhibits osteoblast activity by heterodimerizing with ATF4 to prevent it from binding DNA. It thus appears important to identify and characterize the molecular mechanisms that control Fiat gene expression in osteoblasts. In silico sequence analysis identified a canonical GC-box within a 1,400 bp region of the proximal Fiat gene promoter. Electrophoretic mobility shift assays (EMSA) with MC3T3-E1 osteoblastic cells nuclear extracts indicated that the transcription factors Sp1 and Sp3, but not Sp7/OSTERIX, bound this proximal GC-box. Chromatin immunoprecipitation confirmed interaction of the two transcription factors with the Fiat promoter GC-element in living osteoblasts. Transient transfection studies showed that Sp1 dose-dependently activated the expression of a Fiat-luciferase reporter construct while both the long or short isoforms of Sp3 dose-dependently inhibited transcription from the Fiat reporter construct. Transfection of an Sp7/OSTERIX expression vector did not affect expression of the Fiat-luciferase reporter. Co-transfection of increasing amounts of the Sp3 expression vector in the context of maximal Sp1-dependent Fiat-luciferase activation led to dose-dependent repression of the expression of the reporter. Using RNA knockdown, we measured a reduction in steady-state Fiat expression when Sp1 was inhibited, and a reciprocal increase upon Sp3 knockdown. In parallel, treatment of osteoblasts with WP631, which prevents Sp1/DNA interactions, strongly inhibited the expression of Fiat and reduced the occupancy of the Fiat promoter proximal GC-box by Sp1. Taken together, our results suggest an interplay between Sp1 and Sp3 as a mechanism involved in the control of Fiat gene expression in osteoblasts.

Report this publication

Statistics

Seen <100 times