Immortalized mouse embryo fibroblasts are resistant to miR-290-induced senescence regardless of p53 status

2011 ◽  
Vol 43 (20) ◽  
pp. 1153-1159
Author(s):  
Milena Rizzo ◽  
Monica Evangelista ◽  
Laura Mariani ◽  
Marcella Simili ◽  
Giuseppe Rainaldi ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Mouse Embryo ◽  
Nih3t3 Cells ◽  
Mouse Embryo Fibroblasts ◽  
Primary Mouse ◽  
Murine Fibroblasts ◽  
P53 Status ◽  
Embryo Fibroblasts ◽  
Potential Tumor Suppressor

The prosenescence role of miR-290 and nocodazole has been documented in primary mouse embryo fibroblasts (MEF), while it is not clear whether immortal murine fibroblasts are still responsive to these senescence inducing stimuli. To establish this point, immortal murine fibroblasts with functional (NIH3T3) or nonfunctional p53 (I-MEF) and low levels of miR-290 were tested for their capability to undergo senescence after exposure to either nocodazole or miR-290. Our results clearly indicate that nocodazole induces senescence only in NIH3T3 cells with a functional p53 but not in I-MEF lacking a functional p53. miR-290 overexpression is unable to address any of the tested immortalized clones toward senescence, regardless of the p53 status, suggesting that the prosenescence role of miR-290 is specific for primary but not for immortal murine fibroblasts. Moreover our findings suggest that the mere downregulation of a potential tumor suppressor miRNA in a given cell type does not necessarily imply that it behaves as a tumor suppressor.

scholarly journals Simian Virus 40 Large T Antigen's Association with the CUL7 SCF Complex Contributes to Cellular Transformation

2005 ◽  
Vol 79 (18) ◽  
pp. 11685-11692 ◽  
Author(s):  
Jocelyn S. Kasper ◽  
Hiroshi Kuwabara ◽  
Takehiro Arai ◽  
Syed Hamid Ali ◽  
James A. DeCaprio
Keyword(s):  
Tumor Suppressor ◽  
Mouse Embryo ◽  
Family Members ◽  
Simian Virus 40 ◽  
Cellular Transformation ◽  
Simian Virus ◽  
T Antigen ◽  
Mouse Embryo Fibroblasts ◽  
Embryo Fibroblasts ◽  
F Box Protein

ABSTRACT Simian virus 40 large T antigen (T Ag) is capable of immortalizing and transforming rodent cells. The transforming activity of T Ag is due in large part to perturbation of the tumor suppressor proteins p53 and the retinoblastoma (pRB) family members. Inactivation of these tumor suppressors may not be sufficient for T Ag-mediated cellular transformation. It has been shown that T Ag associates with an SCF-like complex that contains a member of the cullin family of E3 ubiquitin ligases, CUL7, as well as SKP1, RBX1, and an F-box protein, FBXW8. We identified T Ag residues 69 to 83 as required for T Ag binding to the CUL7 complex. We demonstrate that Δ69-83 T Ag, while it lost its ability to associate with CUL7, retained binding to p53 and pRB family members. In the presence of CUL7, wild-type (WT) T Ag but not Δ69-83 T Ag was able to induce proliferation of mouse embryo fibroblasts, an indication of cellular transformation. In contrast, WT and Δ69-83 T Ag enabled mouse embryo fibroblasts to proliferate to similarly high densities in the absence of CUL7. Our data suggest that, in addition to p53 and the pRB family members, T Ag serves to bind to and inactivate the growth-suppressing properties of CUL7. In addition, these results imply that, at least in the presence of T Ag, CUL7 may function as a tumor suppressor.

scholarly journals Differential Expression of Interferon (IFN) Regulatory Factors and IFN-Stimulated Genes at Early Times after West Nile Virus Infection of Mouse Embryo Fibroblasts

2007 ◽  
Vol 81 (21) ◽  
pp. 12005-12018 ◽  
Author(s):  
Svetlana V. Scherbik ◽  
Bronislava M. Stockman ◽  
Margo A. Brinton
Keyword(s):  
West Nile Virus ◽  
Mouse Embryo ◽  
Stress Responses ◽  
Host Response ◽  
West Nile Virus Infection ◽  
West Nile ◽  
Protein Levels ◽  
Mouse Embryo Fibroblasts ◽  
Primary Mouse ◽  
Embryo Fibroblasts

ABSTRACT Although lineage I West Nile virus (WNV) strain Eg101 induced beta interferon (IFN-β) production as early as 12 h after infection in primary mouse embryo fibroblasts and did not inhibit the JAK-STAT signaling pathway, it was still able to replicate efficiently. To gain insights about possible viral countermeasures used by this virus to suppress the host response, the cell transcriptional profile and the kinetics of IFN regulatory factor (IRF) expression and activation were examined at early times after infection. By 12 h after WNV infection, the majority of the up-regulated genes were ones involved in IFN pathways. However, comparison of IFN-stimulated gene (ISG) expression levels in mock-infected, IFN-treated, and virus-infected cells indicated that WNV infection suppressed the up-regulation of a subset of ISGs, including genes involved in transcriptional regulation, apoptosis, and stress responses, prior to 24 h after infection. Analysis of mRNA and protein levels for representative genes indicated that suppression was at the transcriptional and posttranscriptional levels. Translocation of IRF-3 to the nucleus was observed beginning at 8 h, IRF-7 expression was detected by 12 h, but IRF-1 expression was not detected until 24 h after infection. Virus-induced gene suppression was sufficient to overcome the effect of exogenous IFN pretreatment for 1 h but not for 4 h prior to infection. These data indicate that WNV can selectively counteract the host response at early times after infection by previously unreported mechanisms.

Aryl-hydrocarbon receptor is an inhibitory regulator of lipid synthesis and of commitment to adipogenesis

1998 ◽  
Vol 111 (22) ◽  
pp. 3311-3322 ◽  
Author(s):  
D.L. Alexander ◽  
L.G. Ganem ◽  
P. Fernandez-Salguero ◽  
F. Gonzalez ◽  
C.R. Jefcoate
Keyword(s):  
Cell Cycle ◽  
Aryl Hydrocarbon Receptor ◽  
Mouse Embryo ◽  
Biological Effects ◽  
Ppar Gamma ◽  
Glycerol Phosphate ◽  
Aryl Hydrocarbon ◽  
Mouse Embryo Fibroblasts ◽  
Primary Mouse ◽  
Embryo Fibroblasts

The aryl-hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that mediates the biological effects of 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD). In mouse embryo fibroblasts, TCDD activates expression of multiple genes, including CYP1B1, the predominant cytochrome P450 expressed in these cells. Here, we analyze constitutive functions of the AhR in primary mouse embryo fibroblasts (MEFs) and spontaneously immortalized MEF cell lines derived from wild-type (WT) C57BL/6 mice and also from congenic mice with a targeted disruption of the AhR gene (AhR-/-). After multiple passages, primary MEFs exhibit spontaneous differentiation, growth cessation and senescence. Eventually, colonies of immortalized MEFs arise to provide clonal lines. The senescent phase occurs much earlier for AhR-/- MEFs, while immortalization is substantially delayed. Comparison of AhR-/- and WT MEFs also indicates that constitutive AhR activity is required for basal expression of CYP1B1 and suppresses lipogenesis in subconfluent cultures. Primary WT and AhR-/- MEFs and the corresponding lines undergo adipogenesis when treated at confluence with the appropriate hormonal inducers. Addition of TCDD before or concurrent with hormonal induction suppressed PPAR gamma mRNA and adipogenesis, as measured by lipid accumulation, glycerol phosphate dehydrogenase activity and stearoyl CoA desaturase type 1 mRNA expression. This effect of TCDD treatment was absent in AhR-/- MEFs, establishing the role of AhR in hormone-induced adipogenesis. Such hormonal activation of confluent MEFs and preadipocytes results in a limited proliferative expansion followed by irreversible growth arrest. TCDD-treated MEFs undergo the mitotic expansion but fail to exit the cell cycle. In AhR-/- MEFs, there is no such effect of TCDD. These findings implicate the AhR as a constitutive inhibitor of triglyceride synthesis, and as an early regulator of adipocyte differentiation. AhR interference with cell-cycle arrest in differentiation may be linked to the increased rate of senescence.

scholarly journals The p53 Tumor Suppressor Protein Does Not Regulate Expression of Its Own Inhibitor, MDM2, Except under Conditions of Stress

2000 ◽  
Vol 20 (6) ◽  
pp. 2023-2030 ◽  
Author(s):  
Susan M. Mendrysa ◽  
Mary Ellen Perry
Keyword(s):  
Tumor Suppressor ◽  
Mouse Embryo ◽  
Cultured Cells ◽  
Tumor Suppressor Protein ◽  
Dependent Manner ◽  
P53 Tumor Suppressor ◽  
Mouse Embryo Fibroblasts ◽  
Embryo Fibroblasts ◽  
P53 Tumor Suppressor Protein

ABSTRACT MDM2 is an important regulator of the p53 tumor suppressor protein. MDM2 inhibits p53 by binding to it, physically blocking its ability to transactivate gene expression, and stimulating its degradation. In cultured cells, mdm2 expression can be regulated by p53. Hence, mdm2 and p53 can interact to form an autoregulatory loop in which p53 activates expression of its own inhibitor. The p53/MDM2 autoregulatory loop has been elucidated within cultured cells; however, regulation of mdm2 expression by p53 has not been demonstrated within intact tissues. Here, we examine the role of p53 in regulating mdm2 expression in vivo in order to test the hypothesis that the p53/MDM2 autoregulatory loop is the mechanism by which low levels of p53 are maintained. We demonstrate that basal expression of mdm2 in murine tissues is p53 independent, even in tissues that express functional p53. Transcription ofmdm2 is induced in a p53-dependent manner following gamma irradiation, indicating that p53 regulates mdm2 expression in vivo following a stimulus. The requirement for a stimulus to activate p53-dependent regulation of mdm2 expression in vivo appeared to differ from the situation in early-passage mouse embryo fibroblasts, where mdm2 expression is enhanced by the presence of p53. Analysis of mdm2 expression in intact and dispersed embryos revealed that establishment of mouse embryo fibroblasts in culture induces p53-dependent mdm2expression, suggesting that an unknown stimulus activates p53 function in cultured cells. Together, these results indicate that p53 does not regulate expression of its own inhibitor, except in response to stimuli.

scholarly journals Expression of the small T antigen of Lymphotropic Papovavirus is sufficient to transform primary mouse embryo fibroblasts

Virology ◽  
2016 ◽  
Vol 487 ◽  
pp. 112-120 ◽  
Author(s):  
Tushar Gupta ◽  
Maria Teresa Sáenz Robles ◽  
Rachel M. Schowalter ◽  
Christopher B. Buck ◽  
James M. Pipas
Keyword(s):  
Mouse Embryo ◽  
T Antigen ◽  
Mouse Embryo Fibroblasts ◽  
Primary Mouse ◽  
Embryo Fibroblasts ◽  
Small T Antigen ◽  
Lymphotropic Papovavirus

scholarly journals Induction of Alpha/Beta Interferon by Myxoma Virus Is Selectively Abrogated When Primary Mouse Embryo Fibroblasts Become Immortalized

2009 ◽  
Vol 83 (11) ◽  
pp. 5928-5932 ◽  
Author(s):  
Fuan Wang ◽  
John W. Barrett ◽  
Yiyue Ma ◽  
Gregory A. Dekaban ◽  
Grant McFadden
Keyword(s):  
Virus Infection ◽  
Mouse Embryo ◽  
Myxoma Virus ◽  
Virus Challenge ◽  
Beta Interferon ◽  
Phenotypic Alteration ◽  
Mouse Embryo Fibroblasts ◽  
Primary Mouse ◽  
Alpha Beta ◽  
Embryo Fibroblasts

ABSTRACT Mouse embryo fibroblasts (MEFs) are a widely used cell culture system in life sciences, including virology. Here, we show that although primary MEFs are nonpermissive to myxoma virus replication, the corresponding immortalized MEFs support a highly productive myxoma virus infection. We further demonstrate that this permissive phenotype for myxoma virus in immortalized MEFs is due to the immortalization-associated selective block to the cellular alpha/beta interferon induction machinery involved in responding to myxoma virus challenge. Thus, our report presents a clear example, illustrating that a drastic phenotypic alteration can occur with respect to virus infection between primary cells and their immortalized counterparts.

Fusion of Isolated Mitochondria with Tissue Culture Cells

1972 ◽  
Vol 27 (4) ◽  
pp. 419-423 ◽  
Author(s):  
K. Radsak ◽  
W. Sawicki ◽  
H. Koprowski
Keyword(s):  
Tissue Culture ◽  
Mouse Embryo ◽  
Mouse Tumor ◽  
Resistant Mouse ◽  
Isolated Mitochondria ◽  
Culture Cells ◽  
Mouse Embryo Fibroblasts ◽  
Tissue Culture Cells ◽  
Primary Mouse ◽  
Embryo Fibroblasts

Experiments were undertaken to study the effect of introducing isolated mammalian cell mitochondria into tissue culture cells. The DNA of isolated mitochondria was labeled in vitro with 3H-thymidine. Incorporation of 3H-thymidine into mitochondrial DNA was increased tenfold by the addition of bovine serum albumin and sucrose to the assay.Labeled HeLa cell mitochondria were fused with WI38 (human fibroblast) and I-T-22 (Bromodeoxyuridine resistant mouse cell line) cells in the presence of Sendai virus and autoradiographs were made. The results indicated that isolated mitochondria may have been introduced into the cells by the fusion process.Fusion of mitochondria isolated from mouse tumor cell lines with isogenic primary mouse embryo fibroblasts induced permanent growth of these cells in tissue culture, whereas isolated mitochondria of mouse embryo fibroblasts or allogenic tumor cells did not have this effect.

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