Journal Article

Hypoxic repression of STAT1 and its downstream genes by a pVHL/HIF-1 target DEC1/STRA13

Bai, L, Ivanova, A V, Lerman, M I, Salnikow, K, Ivanov, S V

2007

Overview

DEC1/STRA13 is a bHLH type transcriptional regulator involved with immune regulation, hypoxia response and carcinogenesis. We recently demonstrated that STRA13 interacts with STAT3 in the transcriptional activation of STAT-dependent promoters. Here, we pursue STRA13 involvement in the JAK/STAT pathway by studying its role in STAT1 expression. First, we showed that VHL deficiency or HIF-1 activation resulted in the repression of endogenous STAT1 mediated by STRA13. We then characterized the STAT1 proximal promoter to assess its response to STRA13 by transient coexpression in a luciferase reporter assay. Using sequential truncation and site-directed mutagenesis of the STAT1 promoter with STRA13 deletion constructs, we showed that the STRA13 C-terminal trans -activation domain, which is known to bind HDAC1, mostly determines the repressive activity. Involvement of HDAC activity in STAT1 regulation was validated by TSA inhibition and chromatin immunoprecipitation (ChIP) assay. Thus, we demonstrate that STRA13-mediated repression of STAT1 transcription utilizes an HDAC1-dependent mechanism. Furthermore, we show that targets of unphosphorylated STAT1, such as antigen presenting genes and CASP1, are also repressed by hypoxia possibly through the same STRA13-mediated mechanism. Thus, the newly discovered link between HIF-1 and STAT1 reveals a previously unknown role of STRA13 in hypoxia and carcinogenesis.

• Publisher: Nature Publishing Group UK,Nature Publishing,Nature Publishing Group
• Subject: Amino Acid Motifs / Animals / Apoptosis / Base Sequence / Basic Helix-Loop-Helix Transcription Factors - metabolism / Biological and medical sciences / Cancer / Carcinogenesis / Carcinogens / Cell Biology / Cell Hypoxia - genetics / Cell Line / Cell physiology / Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes / Chromatin / Cysteine Endopeptidases - genetics / Cysteine Endopeptidases - metabolism / Down-Regulation / Evaluation / Fundamental and applied biological sciences. Psychology / Gene deletion / Gene Expression Regulation, Neoplastic / Gene silencing / Gene targeting / Genes / Genetic aspects / Genetic regulation / Health aspects / Histone deacetylase / Histone Deacetylases - genetics / Histone Deacetylases - metabolism / Homeodomain Proteins - metabolism / Human Genetics / Humans / Hypoxia / Hypoxia-Inducible Factor 1 - deficiency / Hypoxia-Inducible Factor 1 - genetics / Hypoxia-Inducible Factor 1 - metabolism / Immunoprecipitation / Immunoregulation / Internal Medicine / Medicine / Medicine & Public Health / Mice / Mice, Knockout / Molecular and cellular biology / Molecular Sequence Data / Oncology / original-article / Physiological aspects / Promoter Regions, Genetic - genetics / Properties / Proto-Oncogene Proteins c-myb - genetics / Proto-Oncogene Proteins c-myb - metabolism / Repressor proteins / Signal transduction / Site-directed mutagenesis / Stat1 protein / STAT1 Transcription Factor - genetics / STAT1 Transcription Factor - metabolism / Stat3 protein / Transcription activation / Transcription, Genetic - genetics / Transcriptional Activation / Tumor suppressor genes / VHL protein