STAT3 or USF2 contributes to HIF target gene specificity.

Authors:
Matthew R Pawlus
Matthew R Pawlus
University of Colorado Anschutz Medical Campus
United States
Liyi Wang
Liyi Wang
University of Colorado Anschutz Medical Campus
Aya Murakami
Aya Murakami
Okayama University Graduate School of Medicine
Japan
Guanhai Dai
Guanhai Dai
Institute of Basic Medicine
Dr. Cheng-Jun Hu, PhD
Dr. Cheng-Jun Hu, PhD
University of Colorado
Associate Professor
Pulmonary hypertension
Aurora, CO | United States

PLoS One 2013 21;8(8):e72358. Epub 2013 Aug 21.

Molecular Biology Graduate Program, School of Dental Medicine University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.

The HIF1- and HIF2-mediated transcriptional responses play critical roles in solid tumor progression. Despite significant similarities, including their binding to promoters of both HIF1 and HIF2 target genes, HIF1 and HIF2 proteins activate unique subsets of target genes under hypoxia. The mechanism for HIF target gene specificity has remained unclear. Using siRNA or inhibitor, we previously reported that STAT3 or USF2 is specifically required for activation of endogenous HIF1 or HIF2 target genes. In this study, using reporter gene assays and chromatin immuno-precipitation, we find that STAT3 or USF2 exhibits specific binding to the promoters of HIF1 or HIF2 target genes respectively even when over-expressed. Functionally, HIF1α interacts with STAT3 to activate HIF1 target gene promoters in a HIF1α HLH/PAS and N-TAD dependent manner while HIF2α interacts with USF2 to activate HIF2 target gene promoters in a HIF2α N-TAD dependent manner. Physically, HIF1α HLH and PAS domains are required for its interaction with STAT3 while both N- and C-TADs of HIF2α are involved in physical interaction with USF2. Importantly, addition of functional USF2 binding sites into a HIF1 target gene promoter increases the basal activity of the promoter as well as its response to HIF2+USF2 activation while replacing HIF binding site with HBS from a HIF2 target gene does not change the specificity of the reporter gene. Importantly, RNA Pol II on HIF1 or HIF2 target genes is primarily associated with HIF1α or HIF2α in a STAT3 or USF2 dependent manner. Thus, we demonstrate here for the first time that HIF target gene specificity is achieved by HIF transcription partners that are required for HIF target gene activation, exhibit specific binding to the promoters of HIF1 or HIF2 target genes and selectively interact with HIF1α or HIF2α protein.

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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0072358PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3749168PMC
June 2014
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References

(Supplied by CrossRef)
HIF1alpha and HIF2alpha: sibling rivalry in hypoxic tumour growth and progression
B Keith et al.
Nat Rev Cancer 2012
Oxygen sensing, hypoxia-inducible factor-1 and the regulation of mammalian gene expression
PJ Ratcliffe et al.
J Exp Biol 1998

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