TY - JOUR
T1 - Hepatocyte nuclear factor 3 relieves chromatin-mediated repression of the α-fetoprotein gene
AU - Crowe, Alison J.
AU - Sang, Ling
AU - Li, Kelly Ke
AU - Lee, Kathleen C.
AU - Spear, Brett T.
AU - Barton, Michelle C.
PY - 1999/8/27
Y1 - 1999/8/27
N2 - The α-fetoprotein gene (AFP) is tightly regulated at the tissue- specific level, with expression confined to endoderm-derived cells. We have reconstituted AFP transcription on chromatin-assembled DNA templates in vitro. Our studies show that chromatin assembly is essential for hepatic- specific expression of the AFP gene. While nucleosome-free AFP DNA is robustly transcribed in vitro by both cervical (HeLa) and hepatocellular (HepG2) carcinoma extracts, the general transcription factors and transactivators present in HeLa extract cannot relieve chromatin-mediated repression of AFP. In contrast, preincubation with either HepG2 extract or HeLa extract supplemented with recombinant hepatocyte nuclear factor 3 α (HNF3α), a hepatic-enriched factor expressed very early during liver development, is sufficient to confer transcriptional activation on a chromatin-repressed AFP template. Transient transfection studies illustrate that HNF3α can activate AFP expression in a non-liver cellular environment, confirming a pivotal role for HNF3α in establishing hepatic-specific gene expression. Restriction enzyme accessibility assays reveal that HNF3α promotes the assembly of an open chromatin structure at the AFP promoter. Combined, these functional and structural data suggest that chromatin assembly establishes a barrier to block inappropriate expression of AFP in non-hepatic tissues and that tissue-specific factors, such as HNF3α, are required to alleviate the chromatin-mediated repression.
AB - The α-fetoprotein gene (AFP) is tightly regulated at the tissue- specific level, with expression confined to endoderm-derived cells. We have reconstituted AFP transcription on chromatin-assembled DNA templates in vitro. Our studies show that chromatin assembly is essential for hepatic- specific expression of the AFP gene. While nucleosome-free AFP DNA is robustly transcribed in vitro by both cervical (HeLa) and hepatocellular (HepG2) carcinoma extracts, the general transcription factors and transactivators present in HeLa extract cannot relieve chromatin-mediated repression of AFP. In contrast, preincubation with either HepG2 extract or HeLa extract supplemented with recombinant hepatocyte nuclear factor 3 α (HNF3α), a hepatic-enriched factor expressed very early during liver development, is sufficient to confer transcriptional activation on a chromatin-repressed AFP template. Transient transfection studies illustrate that HNF3α can activate AFP expression in a non-liver cellular environment, confirming a pivotal role for HNF3α in establishing hepatic-specific gene expression. Restriction enzyme accessibility assays reveal that HNF3α promotes the assembly of an open chromatin structure at the AFP promoter. Combined, these functional and structural data suggest that chromatin assembly establishes a barrier to block inappropriate expression of AFP in non-hepatic tissues and that tissue-specific factors, such as HNF3α, are required to alleviate the chromatin-mediated repression.
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U2 - 10.1074/jbc.274.35.25113
DO - 10.1074/jbc.274.35.25113
M3 - Article
C2 - 10455192
AN - SCOPUS:0033609935
SN - 0021-9258
VL - 274
SP - 25113
EP - 25120
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 35
ER -