Hepatocyte Nuclear Factor 4 Gamma Research Articles

Hepatocyte nuclear factor 4 gamma (HNF4G) is correlated with poor prognosis and promotes tumor cell growth by inhibiting caspase-dependent intrinsic apoptosis in colorectal cancer

The hepatocyte nuclear factor 4 gamma (HNF4G), a member of orphan nuclear receptors, is up-regulated and functions as an oncoprotein in a variety of tumors. Recent advances in understanding the biologic function and action mechanism of HNF4G in colorectal cancer (CRC) have not been fully elucidated. In the present study, we observed that HNF4G expression levels were significantly increased in CRC tissues compared with adjacent normal tissues, and HNF4G overexpression correlated with worse prognosis in colorectal cancer. Transfection with a small interference RNA (siRNA) targeting HNF4G in HCT116 and SW480 CRC cell lines significantly inhibited cell proliferation and promoted apoptosis in vitro. In contrast, overexpression of HNF4G increased cell proliferation and decreased the percentage of apoptotic cells. Moreover, we discovered that HNF4G was involved in CRC cell apoptosis via the caspase-dependent intrinsic pathway. Finally, knockdown of HNF4G expression led to attenuated colorectal cancer growth and promoted apoptosis in a xenograft mouse model. Collectively, these results indicate that HNF4G exerts as an oncogenic role in colorectal cancer and provides a potential therapeutic target.

MicroRNA-320b suppresses HNF4G and IGF2BP2 expression to inhibit angiogenesis and tumor growth of lung cancer

We examined the effect of microRNA-320b (miR-320b) on tumor growth and angiogenesis in lung cancer and also determined its downstream molecular mechanisms. Lung cancer tissues and adjacent non-cancerous tissues were collected from 66 patients with lung cancer. miR-320b expression was experimentally determined to be expressed at low level in cancer tissues. The results of gain-of-function experiments suggested that miR-320b overexpression suppressed cancer cell invasion, tube formation, tumor volume and angiogenesis in xenografted nude mice. Hepatocyte nuclear factor 4 gamma (HNF4G) was identified as a target of miR-320b based on in silico analysis. Dual-luciferase reporter gene assays further identified the binding relationship between HNF4G and miR-320b. Lung cancer tissues exhibited increased expression of HNF4G and insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2). Meanwhile, HNF4G knockdown suppressed IGF2BP2 expression, thereby repressing cancer cell invasion and tube formation. Furthermore, IGF2BP2 modified m6A to increase the expression of thymidine kinase 1 (TK1), thus promoting angiogenesis. In nude mice, restoration of TK1 reversed the suppressive effect of miR-320b overexpression on tumor growth rate and CD31 expression. In conclusion, miR-320b suppresses lung cancer growth and angiogenesis by inhibiting HNF4G, IGF2BP2 and TK1.

Expression of HNF4G and its potential functions in lung cancer

The hepatocyte nuclear factor 4 gamma (HNF4G), a member of orphan nuclear receptors, is up-regulated and functions as an oncoprotein in bladder cancer. In the present study, we observed that HNF4G expression was elevated in lung cancer tissues as compared to adjacent normal lung tissues. The expression of HNF4G protein was correlated with the tumor size and the prognosis of patients. Transfection with a small interference RNA (siRNA) targeting HNF4G in two lung cancer cell lines (H358 and H292 cells) significantly inhibited cell proliferation via arresting cells at G1 phase and inducing cell apoptosis. In addition, HNF4G siRNA reduced cell proliferation in a xenograft tumor-bearing model. Moreover, A549 cells, which had relative lower level of HNF4G, were ectopic expressed with HNF4G and treated with an AKT inhibitor (MK-2206). MK-2206 exposure not only attenuated the promoting effects of HNF4G overexpression on cell proliferation and cell cycle progression, but also suppressed the inhibitory effects of HNF4G overexpression on cell apoptosis. These data suggested that AKT signaling pathway was a potential upstream mediator of HNF4G. Collectively, our data indicate that HNF4G exerts as an oncogenic role in lung cancer by promoting cell proliferation and that HNF4G expression is a potential prognosis factor for lung cancer.

Trait‐associated sequence variation in the bovine growth hormone receptor 1A promoter does not affect promoter activity in vitro

Growth hormone (GH) plays a central role in growth and metabolism in cattle by binding to growth hormone receptor (GHR) and stimulating production of insulin-like growth factor 1 (IGF1). Two sequence variations in the promoter transcribing a major GHR mRNA variant, GHR 1A mRNA, have been reported to be associated with quantitative differences in growth rate or blood concentration of IGF1 in cattle. One such variation is in the length of a TG-repeat, being 11 or 16-20; the other variation is in the nucleotide 155 bp upstream from the transcription start site, being G or A. In this study, we determined whether these sequence variations would affect the activity of GHR 1A promoter. We cloned GHR 1A promoters bearing different sequence variations and linked each of them to a reporter gene. Transient transfection analyses revealed that these promoter-reporter constructs did not differ in reporter gene expression. Cotransfection analyses demonstrated that they also did not differ in activation by hepatocyte nuclear factor 4alpha, hepatocyte nuclear factor 4gamma and nuclear receptor subfamily 2 group F member 2, known transcription factors for bovine GHR 1A promoter. These in vitro results, together with a previous observation that neither the nucleotide 155 bp upstream from the transcription start site nor the TG-repeat was part of the GHR 1A promoter region interacting with nuclear proteins from bovine liver, do not support a cause-effect relationship between the reported sequence variations and the associated changes in growth rate or blood IGF1 concentration in cattle.

Chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) and hepatocyte nuclear factor 4gamma (HNF-4gamma) and HNF-4alpha regulate the bovine growth hormone receptor 1A promoter through a common DNA element.

The growth hormone receptor (GHR) 1A promoter is responsible for transcription of the liver-specific GHR mRNA variant 1A in several mammalian species. We previously found that the region between nucleotide -218 and nucleotide -151 (relative to the major transcription start site) of the bovine GHR 1A promoter contained a binding site between -196 and -178 for the liver-enriched transcription factor hepatocyte nuclear factor 4alpha (HNF-4alpha) and that the same region might also interact with additional transcription factors in the liver. Using the -218/-151 region as bait to screen a bovine liver cDNA library in a yeast one-hybrid analysis, we identified chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) and HNF-4gamma, as well as HNF-4alpha, as binding proteins to the -218/-151 region. These binding proteins were also identified in a second yeast one-hybrid analysis using the -196/-178 region as bait, suggesting that COUP-TFII, HNF-4gamma and HNF-4alpha all bind to the -196/-178 region. Electrophoretic mobility shift assays confirmed the ability of these three transcription factors in bovine liver nuclear extracts to interact with the -196/-178 region. These interactions also appeared to exist in vivo, as the GHR 1A promoter containing the -196/-178 region could be recovered by immunoprecipitation of the bovine liver chromatin with antibody against COUP-TFII, HNF-4gamma or HNF-4alpha. In co-transfection analyses, each of these three transcription factors could activate GHR 1A promoter and the activation was dependent on the -196/-178 region. These results together identify COUP-TFII, HNF-4gamma and HNF-4alpha as transcription factors regulating GHR 1A promoter activity through binding to a common DNA element.

Hepatocyte nuclear factor-4gamma: cDNA sequence, gene organization, and mutation screening in early-onset autosomal-dominant type 2 diabetes.

The aim of this study was to investigate whether mutations in hepatocyte nuclear factor (HNF)-4gamma, a transcription factor homologous to HNF-4alpha, contribute to the etiology of early-onset type 2 diabetes. Linkage between diabetes and two polymorphic markers at the HNF-4gamma locus (D8S286 and D8S548) was evaluated in 32 multigenerational families with early-onset autosomal-dominant type 2 diabetes unlinked to known maturity-onset diabetes of the young genes. Total logarithm of odds (LOD) scores were strongly negative (-50.3 at D8S286 and -46.2 at D8S548), but linkage could not be excluded in 15 families having LOD scores >-2.0. To screen these pedigrees for HNF-4gamma mutations, the gene structure was defined. Because reverse transcriptase-polymerase chain reaction experiments indicated that the first 1,674 bp of the published cDNA sequence (3,248 bp) were a cloning artifact, the correct cDNA sequence was determined by 5' rapid amplification of cDNA ends (RACE) and primer extension assay. Based on the new cDNA sequence (1,731 bp), 11 exons were found. After screening the 5' flanking region and all coding exons for mutations, we identified several polymorphisms, one of which affected the amino acid sequence (M190I). However, no mutations segregating with diabetes could be found in these families. We conclude that genetic variability in the HNF-4gamma gene is unlikely to play a major role in the etiology of early-onset autosomal-dominant type 2 diabetes.

Human Hepatocyte Nuclear Factor 4 Isoforms Are Encoded by Distinct and Differentially Expressed Genes

Hepatocyte nuclear factor 4 (HNF4) was first identified as a DNA binding activity in rat liver nuclear extracts. Protein purification had then led to the cDNA cloning of rat HNF4, which was found to be an orphan member of the nuclear receptor superfamily. Binding sites for this factor were identified in many tissue-specifically expressed genes, and the protein was found to be essential for early embryonic development in the mouse. We have now isolated cDNAs encoding the human homolog of the rat and mouse HNF4 splice variant HNF4 alpha 2, as well as a previously unknown splice variant of this protein, which we called HNF alpha 4. More importantly, we also cloned a novel HNF4 subtype (HNF4 gamma) derived from a different gene and showed that the genes encoding HNF 4 alpha and HNF4 gamma are located on human chromosomes 20 and 8, respectively. Northern (RNA) blot analysis revealed that HNF4 GAMMA is expressed in the kidney, pancreas, small intestine, testis, and colon but not in the liver, while HNF4 alpha RNA was found in all of these tissues. By cotransfection experiments in C2 and HeLa cells, we showed that HNF4 gamma is significantly less active than HNF4 alpha 2 and that the novel HNF4 alpha splice variant HNF4 alpha 4 has no detectable transactivation potential. Therefore, the differential expression of distinct HNF4 proteins may play a key role in the differential transcriptional regulation of HNF4-dependent genes.