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Mol. Cell. Biol., Feb 1997, 851-856, Vol 17, No. 2
B Hu, E Wright, L Campbell and KL Blanchard
The erythropoietin (EPO) gene is one of the best examples of a mammalian
gene controlled by oxygen tension. The DNA elements responsible for
hypoxia-induced transcription consist of a short region of the proximal
promoter and a <50-bp 3' enhancer. The elements act cooperatively to
increase the transcriptional initiation rate approximately 100-fold in
response to low oxygen tension in Hep3B cells. Two distinct types of
transactivating proteins have been demonstrated to bind the response
elements in the human EPO enhancer in vitro: one shows hypoxia-inducible
DNA binding activity, while the other activity binds DNA under normoxic and
hypoxic conditions. We have investigated the DNA-protein interactions on
the human EPO enhancer in living tissue culture cells that produce EPO in a
regulated fashion (Hep3B) and in cells that do not express EPO under any
conditions tested (HeLa). We have identified in vivo DNA-protein
interactions on the control elements in the human EPO enhancer by
ligation-mediated PCR technology. We show that the putative protein binding
sites in the EPO enhancer are occupied in vivo under conditions of
normoxia, hypoxia, and cobalt exposure in EPO-producing cells. These sites
are not occupied in cells that do not produce EPO. We also provide evidence
for a conformational change in the topography of the EPO enhancer in
response to hypoxia and cobalt exposure.
Copyright © 1997, American Society for Microbiology
In vivo analysis of DNA-protein interactions on the human erythropoietin enhancer
Center for Excellence in Cancer Research, Treatment and Education, Louisiana State University Medical Center, Shreveport 71130, USA.
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