Transcriptional coactivators CBP and p300 cooperatively enhance HNF-1alpha-mediated expression of the albumin gene in hepatocytes.
Transcriptional coactivators, CREB-binding protein (CBP) and p300, exhibit high homology in structure and similar functions. In the present study, we analyzed the function of CBP and p300 proteins as transcriptional coactivators in the expression of albumin in hepatocytes. The expression levels of CBP and p300 were high in fetal hepatocytes, but low in adult ones. Immunoprecipitation assays showed that both CBP and p300 interacted with hepatocyte nuclear factor-1alpha (HNF-1alpha) in primary hepatocytes. Furthermore, CBP and p300 were co-precipitated without HNF-1alpha. Chromatin immunoprecipitation (ChIP) assays revealed that both CBP and p300 are located in the albumin promoter region in hepatocytes. These results suggested that HNF-1alpha, CBP and p300 were incorporated into a preinitiation complex of RNA polymerase II at the albumin promoter. Luciferase reporter assays showed that CBP and p300 cooperatively triggered HNF-1alpha-mediated transcription of the albumin promoter. In addition, inhibition of CBP or p300 using small interfering RNAs (siRNAs) resulted in a reduction in albumin expression. These results suggest that both CBP and p300 are required for enhanced expression of albumin.
Dohda
Takeaki
T
Department of Biotechnology, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan.
Kaneoka
Hidenori
H
Inayoshi
Yujin
Y
Kamihira
Masamichi
M
Miyake
Katsuhide
K
Iijima
Shinji
S
D000418:Albumins / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D050882:CREB-Binding Protein; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D004268:DNA-Binding Proteins / Q000378:metabolism*; D050881:E1A-Associated p300 Protein; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006367:HeLa Cells; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D022781:Hepatocytes / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008099:Liver / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008297:Male; D009687:Nuclear Proteins / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
D000418:Albumins; D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; C496489:Hnf1a protein, rat; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D015534:Trans-Activators; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D008156:Luciferases; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; C494365:Crebbp protein, rat; D050881:E1A-Associated p300 Protein; C494362:Ep300 protein, rat; D012319:RNA Polymerase II