scholarly journals Loss of p19ARF Eliminates the Requirement for the pRB-Binding Motif in Simian Virus 40 Large T Antigen-Mediated Transformation

2000 ◽  
Vol 20 (20) ◽  
pp. 7624-7633 ◽  
Author(s):  
Herta H. A. Chao ◽  
Ann M. Buchmann ◽  
James A. DeCaprio
Keyword(s):  
Simian Virus 40 ◽  
Cellular Transformation ◽  
Simian Virus ◽  
T Antigen ◽  
Binding Domain ◽  
Large T Antigen ◽  
Wild Type ◽  
J Domain ◽  
Lxcxe Motif ◽  
Inactivating Mutations

ABSTRACT At least three domains of simian virus 40 large T antigen (TAg) participate in cellular transformation. The LXCXE motif of TAg binds to all members of the retinoblastoma protein (pRB) family of tumor suppressors. The N-terminal 70 residues of TAg have significant homology to the J domain of Hsp40/DnaJ and cooperate with the LXCXE motif to inactivate the pRB family. A bipartite C-terminal domain of TAg binds to p53 and thereby disrupts the ability of p53 to act as a sequence-specific transcription factor. The contribution of these three domains of TAg to cellular transformation was evaluated in cells that contained inactivating mutations in the pRB and p53 pathways. Cells that stably expressed wild-type or selected mutant forms of TAg were generated in mouse embryo fibroblasts (MEFs) containing homozygous deletions in the RB, INK4a, and ARFloci. It was determined that the J domain, the LXCXE motif, and the p53-binding domain of TAg were required for full transformation of wild-type and RB −/− MEFs. In contrast,INK4a −/− MEFs that lacked expression of p16 INK4a and p19 ARF andARF −/− MEFs that lacked p19 ARF but expressed p16 INK4a acquired anchorage-independent growth when expressing wild-type TAg or mutant derivatives that disrupted either the pRB-binding or p53-binding domain. The expression and function of the pRB family members were not overly disrupted inARF −/− MEFs expressing LXCXE mutants of TAg. These results suggest that inactivating mutations of p19 ARF can relieve the requirement for the LXCXE motif in TAg-mediated transformation and that TAg may have additional functions in transformation.

scholarly journals Wild-Type p53 Enhances Efficiency of Simian Virus 40 Large-T-Antigen-Induced Cellular Transformation

2009 ◽  
Vol 83 (19) ◽  
pp. 10106-10118 ◽  
Author(s):  
Andrea Hermannstädter ◽  
Christine Ziegler ◽  
Marion Kühl ◽  
Wolfgang Deppert ◽  
Genrich V. Tolstonog
Keyword(s):  
Transformation Efficiency ◽  
Simian Virus 40 ◽  
Transcriptional Regulators ◽  
Cellular Transformation ◽  
Simian Virus ◽  
T Antigen ◽  
Large T Antigen ◽  
Wild Type ◽  
3T3 Cells ◽  
Sv40 Transformation

ABSTRACT Abortive infection of BALB/c mouse embryo fibroblasts differing in p53 gene status (p53+/+ versus p53−/ −) with simian virus 40 (SV40) revealed a quantitatively and qualitatively decreased transformation efficiency in p53−/− cells compared to p53+/+ cells, suggesting a supportive effect of wild-type (wt) p53 in the SV40 transformation process. SV40 transformation efficiency also was low in immortalized p53−/− BALB/c 10-1 cells but could be restored to approximately the level in immortalized p53+/+ BALB/c 3T3 cells by reconstituting wt p53, but not mutant p53 (mutp53), expression. Stable expression of large T antigen (LT) in p53+/+ 3T3 cells resulted in full transformation, while LT expression in p53−/− 10-1 cells could not promote growth in suspension or in soft agar to a significant extent. The helper effect of wt p53 is mediated by its cooperation with LT and resides in the p53 N terminus, as an N-terminally truncated p53 (ΔNp53) could not rescue the p53-null phenotype. The p53 N terminus serves as a scaffold for recruiting transcriptional regulators like p300/CBP and Mdm2 into the LT-p53 complex. Consequently, LT affected global and specific gene expression in p53+/+ cells significantly more than in p53−/− cells. Our data suggest that recruitment of transcriptional regulators into the LT-p53 complex may help to modify cellular gene expression in response to the needs of cellular transformation.

scholarly journals Species-Specific Elements in the Large T-Antigen J Domain Are Required for Cellular Transformation and DNA Replication by Simian Virus 40

2000 ◽  
Vol 20 (15) ◽  
pp. 5749-5757 ◽  
Author(s):  
Christopher S. Sullivan ◽  
James D. Tremblay ◽  
Sheara W. Fewell ◽  
John A. Lewis ◽  
Jeffrey L. Brodsky ◽  
...  
Keyword(s):  
Dna Replication ◽  
Jc Virus ◽  
Simian Virus 40 ◽  
Cellular Transformation ◽  
Simian Virus ◽  
T Antigen ◽  
Large T Antigen ◽  
Sv40 Large T Antigen ◽  
J Domain ◽  
Species Specific

ABSTRACT The J domain of simian virus 40 (SV40) large T antigen is required for efficient DNA replication and transformation. Despite previous reports demonstrating the promiscuity of J domains in heterologous systems, results presented here show the requirement for specific J-domain sequences in SV40 large-T-antigen-mediated activities. In particular, chimeric-T-antigen constructs in which the SV40 T-antigen J domain was replaced with that from the yeast Ydj1p or Escherichia coli DnaJ proteins failed to replicate in BSC40 cells and did not transform REF52 cells. However, T antigen containing the JC virus J domain was functional in these assays, although it was less efficient than the wild type. The inability of some large-T-antigen chimeras to promote DNA replication and elicit cellular transformation was not due to a failure to interact with hsc70, since a nonfunctional chimera, containing the DnaJ J domain, bound hsc70. However, this nonfunctional chimeric T antigen was reduced in its ability to stimulate hsc70 ATPase activity and unable to liberate E2F from p130, indicating that transcriptional activation of factors required for cell growth and DNA replication may be compromised. Our data suggest that the T-antigen J domain harbors species-specific elements required for viral activities in vivo.

scholarly journals Role of pRb-related proteins in simian virus 40 large-T-antigen-mediated transformation.

1995 ◽  
Vol 15 (10) ◽  
pp. 5800-5810 ◽  
Author(s):  
J Zalvide ◽  
J A DeCaprio
Keyword(s):  
Simian Virus 40 ◽  
Cell Types ◽  
Suppressor Gene ◽  
Simian Virus ◽  
T Antigen ◽  
Cellular Proteins ◽  
Large T Antigen ◽  
Wild Type ◽  
Relative Contribution ◽  
Lxcxe Motif

Simian virus 40 large T-antigen (TAg) transformation is thought to be mediated, at least in part, by binding to and modulating the function of certain cellular proteins, including the retinoblastoma tumor suppressor gene product, pRb. TAg can disrupt the inhibitory complexes formed by pRb with the oncogenic transcription factor E2F, and this mechanism has been suggested to be important for TAg-mediated transformation. Residues 102 to 114 of TAg (including the LXCXE motif) are required for binding to pRb. Mutations within this LXCXE motif abolish the ability of TAg to bind to pRb as well as to transform certain cell types. TAg can also bind to at least two other cellular proteins, p107 and p130, that are related to pRb by sequence homology and share the ability to bind E2F. However, whether p107 and p130 are also targets in TAg-mediated transformation is less clear. To assess the relative contribution of the inactivation of pRb, p107, and p130 to transformation by TAg, fibroblasts were prepared from embryos derived from matings of mice heterozygous for an Rb knockout allele. The ability of TAg to transform fibroblasts homozygous for either wild-type or knockout Rb alleles was evaluated. It is demonstrated that the integrity of the LXCXE motif provides a growth advantage in Rb+/+ and Rb-/- cells. Furthermore, wild-type TAg, but not the LXCXE mutants, could bind to p107 and p130 and disrupt p107-E2F and p130-E2F binding complexes. These results suggest that p107 and p130 participate in TAg-mediated transformation and that they may behave as tumor suppressors.

scholarly journals Studies on the origin-specific DNA-binding domain of simian virus 40 large T antigen.

1987 ◽  
Vol 61 (10) ◽  
pp. 3326-3330 ◽  
Author(s):  
M Strauss ◽  
P Argani ◽  
I J Mohr ◽  
Y Gluzman
Keyword(s):  
Dna Binding ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Binding Domain ◽  
Dna Binding Domain ◽  
Large T Antigen

Separation of simian virus 40 large-T-antigen-transforming and origin-binding functions from the ability to block differentiation

1988 ◽  
Vol 8 (3) ◽  
pp. 1380-1384 ◽  
Author(s):  
V Cherington ◽  
M Brown ◽  
E Paucha ◽  
J St Louis ◽  
B M Spiegelman ◽  
...  
Keyword(s):  
Dehydrogenase Activity ◽  
Adipocyte Differentiation ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Lipid Binding ◽  
T Antigen ◽  
Large T Antigen ◽  
Wild Type ◽  
Glycerophosphate Dehydrogenase ◽  
Triglyceride Accumulation

Wild-type simian virus 40 large T antigen is very effective at blocking adipocyte differentiation in 3T3-F442A cells as assayed by triglyceride accumulation, induction of glycerophosphate dehydrogenase activity, and expression of mRNAs for glycerophosphate dehydrogenase, the adipocyte serine protease adipsin, and the putative lipid-binding protein adipocyte P2. Point mutants defective for either origin-specific DNA binding or transformation blocked differentiation as completely as wild type.

scholarly journals Enterocyte Proliferation and Intestinal Hyperplasia Induced by Simian Virus 40 T Antigen Require a Functional J Domain

2007 ◽  
Vol 81 (17) ◽  
pp. 9481-9489 ◽  
Author(s):  
Abhilasha V. Rathi ◽  
M. Teresa Sáenz Robles ◽  
James M. Pipas
Keyword(s):  
Transgenic Mice ◽  
Family Members ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Wild Type ◽  
Morphological Examination ◽  
Enterocyte Proliferation ◽  
J Domain ◽  
Intestinal Hyperplasia

ABSTRACT Transgenic mice expressing the simian virus 40 large T antigen (TAg) in enterocytes develop intestinal hyperplasia that progresses to dysplasia with age. This induction requires TAg action on the retinoblastoma (Rb) family of tumor suppressors and is independent of the p53 pathway. In cell culture systems, the inactivation of Rb proteins requires both a J domain in TAg that interacts with hsc70 and an LXCXE motif that directs association with Rb proteins. Together these elements are sufficient to release E2Fs from their association with Rb family members. We have generated transgenic mice that express a J domain mutant (D44N) in villus enterocytes. In contrast to wild-type TAg, the D44N mutant is unable to induce enterocyte proliferation. Histological and morphological examination revealed that mice expressing the J domain mutant have normal intestines without loss of growth control. Unlike mice expressing wild-type TAg, mice expressing D44N do not reduce the protein levels of p130 and are also unable to dissociate p130-E2F DNA binding complexes. Furthermore, mice expressing D44N in a null p130 background are still unable to develop hyperplasia. These studies demonstrate that the ectopic proliferation of enterocytes by TAg requires a functional J domain and suggest that the J domain is necessary to inactivate all three pRb family members.

scholarly journals Separation of simian virus 40 large-T-antigen-transforming and origin-binding functions from the ability to block differentiation.

1988 ◽  
Vol 8 (3) ◽  
pp. 1380-1384 ◽  
Author(s):  
V Cherington ◽  
M Brown ◽  
E Paucha ◽  
J St Louis ◽  
B M Spiegelman ◽  
...  
Keyword(s):  
Dehydrogenase Activity ◽  
Adipocyte Differentiation ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Lipid Binding ◽  
T Antigen ◽  
Large T Antigen ◽  
Wild Type ◽  
Glycerophosphate Dehydrogenase ◽  
Triglyceride Accumulation

Wild-type simian virus 40 large T antigen is very effective at blocking adipocyte differentiation in 3T3-F442A cells as assayed by triglyceride accumulation, induction of glycerophosphate dehydrogenase activity, and expression of mRNAs for glycerophosphate dehydrogenase, the adipocyte serine protease adipsin, and the putative lipid-binding protein adipocyte P2. Point mutants defective for either origin-specific DNA binding or transformation blocked differentiation as completely as wild type.

scholarly journals The Molecular Chaperone Activity of Simian Virus 40 Large T Antigen Is Required To Disrupt Rb-E2F Family Complexes by an ATP-Dependent Mechanism

2000 ◽  
Vol 20 (17) ◽  
pp. 6233-6243 ◽  
Author(s):  
Christopher S. Sullivan ◽  
Paul Cantalupo ◽  
James M. Pipas
Keyword(s):  
Atp Hydrolysis ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Cellular Growth ◽  
Binding Motif ◽  
Large T Antigen ◽  
Consensus Binding Site ◽  
J Domain ◽  
Immortalized Cell

ABSTRACT The simian virus 40 large T antigen (T antigen) inactivates tumor suppressor proteins and therefore has been used in numerous studies to probe the mechanisms that control cellular growth and to generate immortalized cell lines. Binding of T antigen to the Rb family of growth-regulatory proteins is necessary but not sufficient to cause transformation. The molecular mechanism underlying T-antigen inactivation of Rb function is poorly understood. In this study we show that T antigen associates with pRb and p130-E2F complexes in a stable manner. T antigen dissociates from a p130–E2F-4–DP-1 complex, coincident with the release of p130 from E2F-4–DP-1. The dissociation of this complex requires Hsc70, ATP, and a functional T-antigen J domain. We also report that the “released” E2F–DP-1 complex is competent to bind DNA containing an E2F consensus binding site. We propose that T antigen disrupts Rb-E2F family complexes through the action of its J domain and Hsc70. These findings indicate how Hsc70 supports T-antigen action and help to explain the cisrequirement for a J domain and Rb binding motif in T-antigen-induced transformation. Furthermore, this is the first demonstration linking Hsc70 ATP hydrolysis to the release of E2F bound by Rb family members.

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