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Hepatocyte nuclear factor 1 alpha is expressed in a hamster insulinoma line and transactivates the rat insulin I gene.

ABSTRACT: Systematic mutational analysis previously identified two primary regulatory elements within a minienhancer (-247 to -198) of the rat insulin I promoter that are critical for transcriptional activity. The Far box (-241 to -232) and the FLAT element (-222 to -208) synergistically upregulate transcription and, together, are sufficient to confer tissue-specific and glucose-responsive transcriptional activity on a heterologous promoter. Detailed analysis of the FLAT element further revealed that, in addition to the positive regulatory activity it mediates in tandem with the Far box, it is a site for negative regulatory control. A portion of the FLAT element bears considerable sequence similarity to the consensus binding site for hepatocyte nuclear factor 1 alpha (HNF1 alpha; LF-B1) a liver-enriched homeodomain-containing transcription factor. Here we show that the HNF1-like site within the FLAT element exhibited positive transcriptional activity in both HepG2 and HIT cells and bound similar, but distinguishable, nuclear protein complexes in the respective nuclear extracts. Screening of a hamster insulinoma cDNA library with a PCR-derived probe encompassing the DNA-binding domain of rat HNF1 alpha resulted in isolation of a hamster HNF1 alpha (hHNF1 alpha) cDNA homolog. Specific antiserum identified the HNF1 alpha protein as one component of a specific FLAT-binding complex in HIT nuclear extracts. Expression of the hHNF1 alpha cDNA in COS cells resulted in transactivation of reporter constructs containing multimerized segments of the rat insulin I minienhancer. Thus, HNF1 alpha, one component of a DNA-binding complex involved in transcriptional regulation of the rat insulin I gene, may play a significant role in nonhepatic as well as hepatic gene transcription.

SUBMITTER: Emens LA

PROVIDER: S-EPMC49697 | biostudies-other | 1992 Aug

REPOSITORIES: biostudies-other

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Hepatocyte nuclear factor 1 alpha is expressed in a hamster insulinoma line and transactivates the rat insulin I gene.

Emens L A LA Landers D W DW Moss L G LG

Proceedings of the National Academy of Sciences of the United States of America 19920801 16

Systematic mutational analysis previously identified two primary regulatory elements within a minienhancer (-247 to -198) of the rat insulin I promoter that are critical for transcriptional activity. The Far box (-241 to -232) and the FLAT element (-222 to -208) synergistically upregulate transcription and, together, are sufficient to confer tissue-specific and glucose-responsive transcriptional activity on a heterologous promoter. Detailed analysis of the FLAT element further revealed that, in ...[more]

PMID: 1380153

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Project description:AIM:To uncover the role of hepatocyte nuclear factor 4 alpha (HNF4?) in regulating hepatic expression of microRNAs. METHODS:Microarray and real-time PCR were used to determine hepatic expression of microRNAs in young-adult mice lacking Hnf4? expression in liver (Hnf4?-LivKO). Integrative genomics viewer software was used to analyze the public chromatin immunoprecipitation-sequencing datasets for DNA-binding of HNF4?, RNA polymerase-II, and histone modifications to loci of microRNAs in mouse liver and human hepatoma cells. Dual-luciferase reporter assay was conducted to determine effects of HNF4? on the promoters of mouse and human microRNAs as well as effects of microRNAs on the untranslated regions (3'UTR) of two genes in human hepatoma cells. RESULTS:Microarray data indicated that most microRNAs remained unaltered by Hnf4? deficiency in Hnf4?-LivKO mice. However, certain liver-predominant microRNAs were down-regulated similarly in young-adult male and female Hnf4?-LivKO mice. The down-regulation of miR-101, miR-192, miR-193a, miR-194, miR-215, miR-802, and miR-122 as well as induction of miR-34 and miR-29 in male Hnf4?-LivKO mice were confirmed by real-time PCR. Analysis of public chromatin immunoprecipitation-sequencing data indicates that HNF4? directly binds to the promoters of miR-101, miR-122, miR-194-2/miR-192 and miR-193, which is associated with histone marks of active transcription. Luciferase reporter assay showed that HNF4? markedly activated the promoters of mouse and human miR-101b/miR-101-2 and the miR-194/miR-192 cluster. Additionally, miR-192 and miR-194 significantly decreased activities of luciferase reporters for the 3'UTR of histone H3F3 and chromodomain helicase DNA binding protein 1 (CHD1), respectively, suggesting that miR-192 and miR-194 might be important in chromosome remodeling through directly targeting H3F3 and CHD1. CONCLUSION:HNF4? is essential for hepatic basal expression of a group of liver-enriched microRNAs, including miR-101, miR-192, miR-193a, miR-194 and miR-802, through which HNF4? may play a major role in the post-transcriptional regulation of gene expression and maintenance of the epigenome in liver.

Dataset Information

Hepatocyte nuclear factor 1 alpha is expressed in a hamster insulinoma line and transactivates the rat insulin I gene.

Publications

Hepatocyte nuclear factor 1 alpha is expressed in a hamster insulinoma line and transactivates the rat insulin I gene.

Similar Datasets

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