scholarly journals A domain of methylation change at the albumin locus in rat hepatoma cell variants.

1985 ◽  
Vol 5 (1) ◽  
pp. 214-225 ◽  
Author(s):  
A Orlofsky ◽  
L A Chasin
Keyword(s):  
De Novo ◽  
Hepatoma Cell ◽  
Northern Blotting ◽  
Cell Protein ◽  
Hepatoma Cell Line ◽  
Mrna Levels ◽  
Albumin Production ◽  
Albumin Mrna ◽  
Rat Hepatoma ◽  
De Novo Methylation

A well-differentiated rat hepatoma cell line, Fu5-5, yields variant clones whose rate of secretion of serum albumin ranges from 40 to less than 0.08 micrograms of albumin/mg of cell protein per 48 h. Clones were classified as high producers (10 to 40 micrograms/mg per 48 h), intermediate producers (1 to 10 micrograms/mg per 48 h), low producers (0.1 to 1.0 micrograms/mg per 48 h), and null variants (less than 0.1 micrograms/mg per 48 h). Albumin synthetic rates are proportional to secretion rates and range from 0.9 to less than 0.002% of total protein synthesis as measured by pulse-labeling. Steady-state albumin mRNA levels were measured by filter hybridization of fragmented, end-labeled mRNA and by Northern blotting. Message levels are proportional to albumin synthetic rates except for a high producer in which albumin mRNA is less elevated than the synthetic rate. The extent of methylation was quantitated at each of 24 CpG-containing sites or site clusters at the albumin locus. These sites span a region that contains the albumin gene as well as 10 kilobases of the 5' flank and 1 kilobase of the 3' flank. An 8-kilobase region is described, with boundaries in the 5' flank and in the middle of the gene, within which all 11 sites examined showed a correlation of undermethylation with the high-producer phenotype. In contrast, 12 of 13 sites outside of this region showed no phenotype correlation. Null variants derived from a high producer underwent de novo methylation of this domain. Six independent hybrid clones derived from the cross of a high producer with a null variant showed extinction of albumin production and hypermethylation of the domain. Apparently these cells retain the capacity for the de novo methylation of these specific sites.

A domain of methylation change at the albumin locus in rat hepatoma cell variants

1985 ◽  
Vol 5 (1) ◽  
pp. 214-225
Author(s):  
A Orlofsky ◽  
L A Chasin
Keyword(s):  
De Novo ◽  
Hepatoma Cell ◽  
Northern Blotting ◽  
Cell Protein ◽  
Hepatoma Cell Line ◽  
Mrna Levels ◽  
Albumin Production ◽  
Albumin Mrna ◽  
Rat Hepatoma ◽  
De Novo Methylation

A well-differentiated rat hepatoma cell line, Fu5-5, yields variant clones whose rate of secretion of serum albumin ranges from 40 to less than 0.08 micrograms of albumin/mg of cell protein per 48 h. Clones were classified as high producers (10 to 40 micrograms/mg per 48 h), intermediate producers (1 to 10 micrograms/mg per 48 h), low producers (0.1 to 1.0 micrograms/mg per 48 h), and null variants (less than 0.1 micrograms/mg per 48 h). Albumin synthetic rates are proportional to secretion rates and range from 0.9 to less than 0.002% of total protein synthesis as measured by pulse-labeling. Steady-state albumin mRNA levels were measured by filter hybridization of fragmented, end-labeled mRNA and by Northern blotting. Message levels are proportional to albumin synthetic rates except for a high producer in which albumin mRNA is less elevated than the synthetic rate. The extent of methylation was quantitated at each of 24 CpG-containing sites or site clusters at the albumin locus. These sites span a region that contains the albumin gene as well as 10 kilobases of the 5' flank and 1 kilobase of the 3' flank. An 8-kilobase region is described, with boundaries in the 5' flank and in the middle of the gene, within which all 11 sites examined showed a correlation of undermethylation with the high-producer phenotype. In contrast, 12 of 13 sites outside of this region showed no phenotype correlation. Null variants derived from a high producer underwent de novo methylation of this domain. Six independent hybrid clones derived from the cross of a high producer with a null variant showed extinction of albumin production and hypermethylation of the domain. Apparently these cells retain the capacity for the de novo methylation of these specific sites.

A distinct glucocorticoid hormone response regulates phosphoprotein maturation in rat hepatoma cells

1986 ◽  
Vol 6 (2) ◽  
pp. 574-585
Author(s):  
K Karlsen ◽  
A K Vallerga ◽  
J Hone ◽  
G L Firestone
Keyword(s):  
Receptor Binding ◽  
De Novo ◽  
Hepatoma Cell ◽  
Hepatoma Cell Line ◽  
Hormone Response ◽  
Absolute Level ◽  
Chase Period ◽  
Glucocorticoid Hormone ◽  
Tumor Virus ◽  
Rat Hepatoma

Glucocorticoid hormone-dependent maturation of the mouse mammary tumor virus (MMTV) phosphorylated polyprotein (Pr74) allows experimental access to certain posttranslational regulatory circuits under steroid control in M1.54 cells, an MMTV-infected rat hepatoma cell line. Pulse-chase experiments revealed that [35S]methionine-labeled Pr74 synthesized in uninduced cells could be converted posttranslationally into p24, a stable phosphorylated maturation product, only after 4 h of exposure to 1 microM dexamethasone, a synthetic glucocorticoid. This regulated processing could be prevented by prior exposure, during the chase period, to inhibitors of RNA (actinomycin D) or protein (cycloheximide or puromycin) synthesis. Moreover, half-maximal production of p24 occurred at 10 nM dexamethasone, a concentration that approximated half-maximal receptor binding and stimulation of MMTV transcript synthesis. Kinetic, hormonal, and genetic evidence suggest that p24 expression did not require or result from the overall glucocorticoid-dependent increase in polyprotein concentration. First, 20 h after dexamethasone withdrawal, Pr74 maturation was completely deinduced, whereas the absolute level of this MMTV precursor remained 10-fold over its basal level. Second, progesterone, which competes with dexamethasone for receptor binding, facilitated the regulated production of p24 but prevented the steroid-mediated accumulation of functional MMTV mRNA. Lastly, certain glucocorticoid-responsive variants, derived from M1.54 cells by resistance to complement cytolysis, expressed p24 in the presence or absence of glucocorticoid-induced levels of Pr74. Taken together, our results suggest that the glucocorticoid-regulated maturation of MMTV phosphopolyproteins resulted from an independent hormone response that required normal receptor function and de novo RNA and protein synthesis.

scholarly journals A distinct glucocorticoid hormone response regulates phosphoprotein maturation in rat hepatoma cells.

1986 ◽  
Vol 6 (2) ◽  
pp. 574-585 ◽  
Author(s):  
K Karlsen ◽  
A K Vallerga ◽  
J Hone ◽  
G L Firestone
Keyword(s):  
Receptor Binding ◽  
De Novo ◽  
Hepatoma Cell ◽  
Hepatoma Cell Line ◽  
Hormone Response ◽  
Absolute Level ◽  
Chase Period ◽  
Glucocorticoid Hormone ◽  
Tumor Virus ◽  
Rat Hepatoma

Glucocorticoid hormone-dependent maturation of the mouse mammary tumor virus (MMTV) phosphorylated polyprotein (Pr74) allows experimental access to certain posttranslational regulatory circuits under steroid control in M1.54 cells, an MMTV-infected rat hepatoma cell line. Pulse-chase experiments revealed that [35S]methionine-labeled Pr74 synthesized in uninduced cells could be converted posttranslationally into p24, a stable phosphorylated maturation product, only after 4 h of exposure to 1 microM dexamethasone, a synthetic glucocorticoid. This regulated processing could be prevented by prior exposure, during the chase period, to inhibitors of RNA (actinomycin D) or protein (cycloheximide or puromycin) synthesis. Moreover, half-maximal production of p24 occurred at 10 nM dexamethasone, a concentration that approximated half-maximal receptor binding and stimulation of MMTV transcript synthesis. Kinetic, hormonal, and genetic evidence suggest that p24 expression did not require or result from the overall glucocorticoid-dependent increase in polyprotein concentration. First, 20 h after dexamethasone withdrawal, Pr74 maturation was completely deinduced, whereas the absolute level of this MMTV precursor remained 10-fold over its basal level. Second, progesterone, which competes with dexamethasone for receptor binding, facilitated the regulated production of p24 but prevented the steroid-mediated accumulation of functional MMTV mRNA. Lastly, certain glucocorticoid-responsive variants, derived from M1.54 cells by resistance to complement cytolysis, expressed p24 in the presence or absence of glucocorticoid-induced levels of Pr74. Taken together, our results suggest that the glucocorticoid-regulated maturation of MMTV phosphopolyproteins resulted from an independent hormone response that required normal receptor function and de novo RNA and protein synthesis.

Effects of diabetes and insulin on betaine-homocysteine S-methyltransferase expression in rat liver

2006 ◽  
Vol 290 (5) ◽  
pp. E933-E939 ◽  
Author(s):  
Shobhitha Ratnam ◽  
Enoka P. Wijekoon ◽  
Beatrice Hall ◽  
Timothy A. Garrow ◽  
Margaret E. Brosnan ◽  
...  
Keyword(s):  
Cell Line ◽  
De Novo ◽  
Hepatoma Cell ◽  
Major Complication ◽  
Diabetic Rats ◽  
Plasma Homocysteine ◽  
Hepatoma Cell Line ◽  
Mrna Levels ◽  
Transsulfuration Pathway ◽  
Betaine Homocysteine Methyltransferase

Elevation of plasma homocysteine levels has been recognized as an independent risk factor for the development of cardiovascular disease, a major complication of diabetes. Plasma homocysteine reflects a balance between its synthesis via S-adenosyl-l-methionine-dependent methylation reactions and its removal through the transmethylation and the transsulfuration pathways. Betaine-homocysteine methyltransferase (BHMT, EC 2.1.1.5 ) is one of the enzymes involved in the remethylation pathway. BHMT, a major zinc metalloenzyme in the liver, catalyzes the transfer of methyl groups from betaine to homocysteine to form dimethylglycine and methionine. We have previously shown that plasma homocysteine levels and the transsulfuration pathway are affected by diabetes. In the present study, we found increased BHMT activity and mRNA levels in livers from streptozotocin-diabetic rats. In the rat hepatoma cell line (H4IIE cells), glucocorticoids (triamcinolone) increased the level and rate of BHMT mRNA synthesis. In the same cell line, insulin decreased the abundance of BHMT mRNA and the rate of de novo mRNA transcription of the gene. Thus the decreased plasma homocysteine in various models of diabetes could be due to enhanced homocysteine removal brought about by a combination of increased transsulfuration of homocysteine to cysteine and increased remethylation of homocysteine to methionine by BHMT.

scholarly journals The coordinated regulation of fibrinogen gene transcription by hepatocyte-stimulating factor and dexamethasone.

1987 ◽  
Vol 105 (3) ◽  
pp. 1067-1072 ◽  
Author(s):  
J M Otto ◽  
H E Grenett ◽  
G M Fuller
Keyword(s):  
Hepatoma Cell ◽  
Rat Hepatocytes ◽  
In Vitro Transcription ◽  
Cell Protein ◽  
Hepatoma Cell Line ◽  
Mrna Levels ◽  
Rat Hepatoma Cell Line ◽  
Stimulating Factor ◽  
Quantitation Of Mrna

Glucocorticoids and hepatocyte-stimulating factor (HSF; a monocyte/macrophage-derived polypeptide) are potent regulators of fibrinogen biosynthesis. Using primary rat hepatocytes and a rat hepatoma cell line (FAZA) we have determined, more precisely, the interaction between these two molecules in the control of fibrinogen production. When dexamethasone (DEX) or HSF is added to the cells, there is a substantial increase in fibrinogen production (1.5-3-fold). However, if both agents are administered simultaneously the response is much greater with a 15-20-fold rise in synthesis. Quantitative RNA analysis demonstrates that when the factors are present individually only HSF elevates fibrinogen mRNA levels, but the effect is much enhanced in the presence of DEX. This pattern is also seen in the results of the in vitro transcription assays which allow quantitation of mRNA synthesis in isolated nuclei. Cycloheximide does not significantly interfere with the increased transcription brought about by HSF in either cell type. However, the DEX enhancement is blocked by cycloheximide in FAZA cells, thus indicating that in the transformed cell protein synthesis is required for maximal transcription to occur. Data presented here demonstrates the requirement for two types of regulator molecules in the control of fibrinogen gene expression; a polypeptide hormone (HSF) that increases transcription and a steroid (DEX) that enhances the action of the polypeptide.

Endothelial Cell Protein S Synthesis Is Upregulated by the Complex of IL-6 and Soluble IL-6 Receptor

1997 ◽  
Vol 77 (05) ◽  
pp. 1014-1019 ◽  
Author(s):  
W Craig Hooper ◽  
Donald J Phillips ◽  
Bruce L Evatt
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Cell Line ◽  
Neutralizing Antibodies ◽  
Hepatoma Cell ◽  
Protein S ◽  
Oncostatin M ◽  
Cell Protein ◽  
Microvascular Endothelial Cell ◽  
Hepatoma Cell Line

SummaryWe have recently demonstrated that the proinflammatory cytokine, interleukin-6 (IL-6), could upregulate the production of protein S in the human hepatoma cell line, HepG-2, but not in endothelial cells. In this study, we have demonstrated that the combination of exogenous IL-6 and soluble IL-6 receptor (sIL-6R) could significantly upregulate protein S production in both primary human umbilical vein endothelial cells (HUVEC) and in the immortalized human microvascular endothelial cell line, HMEC-1. The IL-6/sIL-6R complex was also able to rapidly induce tyrosine phosphorylation of the IL-6 transducer, gpl30. Neutralizing antibodies directed against either IL-6 or gpl30 blocked protein S upregulation by the IL-6/sIL-6R complex. It was also observed that exogenous sIL-6R could also upregulate protein S by forming a complex with IL-6 constitutively produced by the endothelial cell. Two other cytokines which also utilize the gpl30 receptor, oncostatin M (OSM) and leukemia inhibitory factor (LIF), were also able to upregulate endothelial cell protein S. This study demonstrates a mechanism that allows endothelial cells to respond to IL-6 and also illustrates the potential importance of circulating soluble receptors in the regulation of the anticoagulation pathway.

scholarly journals Stimulation of de novo glutathione synthesis by nitrofurantoin for enhanced resilience of hepatocytes

2021 ◽  
Author(s):  
Lukas S. Wijaya ◽  
Carina Rau ◽  
Theresa S. Braun ◽  
Serif Marangoz ◽  
Vincent Spegg ◽  
...  
Keyword(s):  
De Novo ◽  
Hepatoma Cell ◽  
Proteasome Inhibitors ◽  
Essential Element ◽  
Hepatoma Cell Line ◽  
Related Factor ◽  
Human Hepatoma Cell ◽  
Intact Cells ◽  
Intracellular Glutathione ◽  
Endogenous Antioxidant

AbstractToxicity is not only a function of damage mechanisms, but is also determined by cellular resilience factors. Glutathione has been reported as essential element to counteract negative influences. The present work hence pursued the question how intracellular glutathione can be elevated transiently to render cells more resistant toward harmful conditions. The antibiotic nitrofurantoin (NFT) was identified to stimulate de novo synthesis of glutathione in the human hepatoma cell line, HepG2, and in primary human hepatocytes. In intact cells, activation of NFT yielded a radical anion, which subsequently initiated nuclear-factor-erythroid 2-related-factor-2 (Nrf2)-dependent induction of glutamate cysteine ligase (GCL). Application of siRNA-based intervention approaches confirmed the involvement of the Nrf2-GCL axis in the observed elevation of intracellular glutathione levels. Quantitative activation of Nrf2 by NFT, and the subsequent rise in glutathione, were similar as observed with the potent experimental Nrf2 activator diethyl maleate. The elevation of glutathione levels, observed even 48 h after withdrawal of NFT, rendered cells resistant to different stressors such as the mitochondrial inhibitor rotenone, the redox cycler paraquat, the proteasome inhibitors MG-132 or bortezomib, or high concentrations of NFT. Repurpose of the antibiotic NFT as activator of Nrf2 could thus be a promising strategy for a transient and targeted activation of the endogenous antioxidant machinery.

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