Cooperative Interaction of EWS with CREB-binding Protein Selectively Activates Hepatocyte Nuclear Factor 4-mediated Transcription

HNF-4 (hepatocyte nuclear factor 4) is a key regulator of liver-specific gene expression in mammals. We have shown previously that the activity of the human APOC3 (apolipoprotein C-III) promoter is positively regulated by the anti-inflammatory cytokine TGFβ (transforming growth factor β) and its effectors Smad3 (similar to mothers against decapentaplegic 3) and Smad4 proteins via physical and functional interactions between Smads and HNF-4. We now show that the pro-inflammatory cytokine TNFα (tumour necrosis factor α) antagonizes TGFβ for the regulation of APOC3 gene expression in hepatocytes. TNFα was a strong inhibitor of the activity of apolipoprotein promoters that harbour HNF-4 binding sites and this inhibition required HNF-4. Using specific inhibitors of TNFα-induced signalling pathways, it was shown that inhibition of the APOC3 promoter by TNFα involved NF-κB (nuclear factor κB). Latent membrane protein 1 of the Epstein–Barr virus, which is an established potent activator of NF-κB as well as wild-type forms of various NF-κB signalling mediators, also inhibited strongly the APOC3 promoter and the transactivation function of HNF-4. TNFα had no effect on the stability or the nuclear localization of HNF-4 in HepG2 cells, but inhibited the binding of HNF-4 to the proximal APOC3 HRE (hormone response element). Using the yeast-transactivator-GAL4 system, we showed that both AF-1 and AF-2 (activation functions 1 and 2) of HNF-4 are inhibited by TNFα and that this inhibition was abolished by overexpression of different HNF-4 co-activators, including PGC-1 (peroxisome-proliferator-activated-receptor-γ co-activator 1), CBP [CREB (cAMP-response-element-binding protein) binding protein] and SRC3 (steroid receptor co-activator 3). In summary, our findings indicate that TNFα, or other factors that trigger an NF-κB response in hepatic cells, inhibit the transcriptional activity of the APOC3 and other HNF-4-dependent promoters and that this inhibition could be accounted for by a decrease in DNA binding and the down-regulation of the transactivation potential of the AF-1 and AF-2 domains of HNF-4.

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GATA binding protein 4 promotes the expression and transcription of hepatitis B virus by facilitating hepatocyte nuclear factor 4 alpha in vitro

Virology Journal ◽

10.1186/s12985-021-01668-z ◽

2021 ◽

Vol 18 (1) ◽

Author(s):

Xiaoqin Lv ◽

Xia Xiang ◽

Yue Wu ◽

Yang Liu ◽

Ruqing Xu ◽

...

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Binding Protein ◽

Nuclear Factor ◽

Hepatocyte Nuclear Factor ◽

B Virus ◽

Hepatocyte Nuclear Factor 4 ◽

Positive Effect

Abstract Background GATA binding protein 4 (GATA4) has been reported as a potential target of gene therapy for hepatocellular carcinoma (HCC). It is well known that the main cause of HCC is the chronic infection of hepatitis B virus (HBV). However, whether the effect of GATA4 on HBV has not yet been reported. Methods In this study, the regulation of GATA4 on HBV was analyzed in vitro. In turn, the effect of HBV on GATA4 was also observed in vitro, in vivo, and clinical HCC patients. Subsequently, we analyzed whether the effect of GATA4 on HBV was related to hepatocyte nuclear factor 4 alpha (HNF4α) in vitro. Results The results showed that GATA4 significantly promoted the secretion of HBV surface antigen (HBsAg) and HBV e antigen in the cell culture medium, improved the replication of HBV genomic DNA, and increased the level of HBV 3.5 kb pre-genomic RNA and HBV total RNA (P < 0.05). Moreover, it was showed that HBV had no significant effect on GATA4 in vitro and in vivo (P > 0.05). At the same time, GATA4 expression was decreased in 78.9% (15/19) of HCC patients regardless of the HBV and HBsAg status. Among them, there were 76.9% (10/13) in HBV-associated patients with HCC (HBV-HCC), and 83.3% (5/6) in non-HBV-HCC patients. In addition, the expression of HNF4α was also up-regulated or down-regulated accordingly when stimulating or interfering with the expression of GATA4. Furthermore, stimulating the expression of HNF4α could only alleviate the HBsAg level and HBV transcription levels, but had no significant effect on GATA4. Conclusions In summary, this study found that GATA4 has a positive effect on HBV, and the potential pathway may be related to another transcription factor HNF4α that regulates HBV.

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Sterol Regulatory Element-binding Protein-2 Interacts with Hepatocyte Nuclear Factor-4 to Enhance Sterol Isomerase Gene Expression in Hepatocytes

Journal of Biological Chemistry ◽

10.1074/jbc.m302387200 ◽

2003 ◽

Vol 278 (38) ◽

pp. 36176-36182 ◽

Cited By ~ 51

Author(s):

Koichi Misawa ◽

Taro Horiba ◽

Naoto Arimura ◽

Yuko Hirano ◽

Jun Inoue ◽

...

Keyword(s):

Gene Expression ◽

Binding Protein ◽

Regulatory Element ◽

Nuclear Factor ◽

Hepatocyte Nuclear Factor ◽

Element Binding Protein ◽

Sterol Regulatory Element ◽

Hepatocyte Nuclear Factor 4

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The activation function-1 of hepatocyte nuclear factor-4 is an acidic activator that mediates interactions through bulky hydrophobic residues

Biochemical Journal ◽

10.1042/bj3560635 ◽

2001 ◽

Vol 356 (2) ◽

pp. 635-642 ◽

Cited By ~ 7

Author(s):

Elena KISTANOVA ◽

Helen DELL ◽

Panayota TSANTILI ◽

Eileen FALVEY ◽

Christos CLADARAS ◽

...

Keyword(s):

Amino Acids ◽

Transcription Factors ◽

Binding Protein ◽

Activation Function ◽

Transcriptional Analysis ◽

Nuclear Factor ◽

Hepatocyte Nuclear Factor ◽

Hydrophobic Residues ◽

Charged Residues ◽

Hepatocyte Nuclear Factor 4

The hepatocyte nuclear factor-4 (HNF-4) contains two transcription activation domains. One domain, activation function-1 (AF-1), consists of the extreme N-terminal 24 amino acids and functions as a constitutive autonomous activator of transcription. This short transactivator belongs to the class of acidic activators, and it is predicted to adopt an amphipathic α-helical structure. Transcriptional analysis of sequential point mutations of the negatively charged residues (Asp and Glu) revealed a stepwise decrease in activity, while mutation of all acidic residues resulted in complete loss of transcriptional activity. Mutations of aromatic and hydrophobic amino acids surrounding the negatively charged residues had a much more profound effect than mutations of acidic amino acids, since even a single mutation of these residues resulted in a dramatic decrease in transactivation, thus demonstrating the importance of hydrophobic residues in AF-1 activity. Like other acidic activators, the AF-1 of HNF-4 binds the transcription factor IIB and the TATA-binding protein directly in vitro. In addition, the cAMP-response-element-binding-protein, a transcriptional adapter involved in the transactivation of a plethora of transcription factors, interacts with the AF-1 of HNF-4 and co-operates in the process of transactivation by HNF-4. The different protein targets of AF-1 suggest that the AF-1 of HNF-4 may be involved in recruiting both general transcription factors and chromatin remodelling proteins during activation of gene expression.

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