scholarly journals Multiple functional domains of human U2 small nuclear RNA: strengthening conserved stem I can block splicing.

1992 ◽  
Vol 12 (12) ◽  
pp. 5464-5473 ◽  
Author(s):  
J Wu ◽  
J L Manley
Keyword(s):  
Simian Virus 40 ◽  
Suppressor Gene ◽  
Simian Virus ◽  
T Antigen ◽  
Compensatory Mutation ◽  
Base Pairing ◽  
Recognition Sequence ◽  
Site Mutation ◽  
U6 Snrna ◽  
Branch Site

We showed previously that a branch site mutation in simian virus 40 early pre-mRNA that prevented small t antigen mRNA splicing could be efficiently suppressed by a compensatory mutation in a coexpressed U2 small nuclear (sn) RNA gene. We have now generated second-site mutations in this suppressor gene to investigate regions of U2 RNA required for function. A number of mutations in a putative stem at the 5' end of the molecule inhibited splicing, indicating that bases in this region are important for activity. However, several lines of evidence suggested that formation of the entire stem is not essential for splicing. Indeed, mutations that strengthen the stem actually inhibited splicing, and evidence that this prevents a required base-pairing interaction with U6 snRNA is presented. These results suggest that the relative stabilities of competing intra- and intermolecular base-pairing interactions play an important role in the splicing reaction. Mutations in a conserved single-stranded region immediately 3' to the branch site recognition sequence all inhibited splicing, indicating that this region is required for U2 function, although its exact role remains unknown. Finally, two mutations in the loop of stem IV at the 3' end of the molecule, which destroy the binding site of U2 sn ribonucleoprotein B", prevented small t splicing; this finding contrasts with previous studies which utilized different assay systems. Analysis of the accumulation and subcellular localization of all of the mutant RNAs showed that they were similar to those of the parental suppressor U2 RNA, indicating that the effects observed indeed reflect defects in splicing.

scholarly journals Multiple functional domains of human U2 small nuclear RNA: strengthening conserved stem I can block splicing

1992 ◽  
Vol 12 (12) ◽  
pp. 5464-5473
Author(s):  
J Wu ◽  
J L Manley
Keyword(s):  
Simian Virus 40 ◽  
Suppressor Gene ◽  
Simian Virus ◽  
T Antigen ◽  
Compensatory Mutation ◽  
Base Pairing ◽  
Recognition Sequence ◽  
Site Mutation ◽  
U6 Snrna ◽  
Branch Site

We showed previously that a branch site mutation in simian virus 40 early pre-mRNA that prevented small t antigen mRNA splicing could be efficiently suppressed by a compensatory mutation in a coexpressed U2 small nuclear (sn) RNA gene. We have now generated second-site mutations in this suppressor gene to investigate regions of U2 RNA required for function. A number of mutations in a putative stem at the 5' end of the molecule inhibited splicing, indicating that bases in this region are important for activity. However, several lines of evidence suggested that formation of the entire stem is not essential for splicing. Indeed, mutations that strengthen the stem actually inhibited splicing, and evidence that this prevents a required base-pairing interaction with U6 snRNA is presented. These results suggest that the relative stabilities of competing intra- and intermolecular base-pairing interactions play an important role in the splicing reaction. Mutations in a conserved single-stranded region immediately 3' to the branch site recognition sequence all inhibited splicing, indicating that this region is required for U2 function, although its exact role remains unknown. Finally, two mutations in the loop of stem IV at the 3' end of the molecule, which destroy the binding site of U2 sn ribonucleoprotein B", prevented small t splicing; this finding contrasts with previous studies which utilized different assay systems. Analysis of the accumulation and subcellular localization of all of the mutant RNAs showed that they were similar to those of the parental suppressor U2 RNA, indicating that the effects observed indeed reflect defects in splicing.

Antibodies specific for the human retinoblastoma protein identify a family of related polypeptides

1991 ◽  
Vol 11 (11) ◽  
pp. 5792-5799
Author(s):  
Q J Hu ◽  
C Bautista ◽  
G M Edwards ◽  
D Defeo-Jones ◽  
R E Jones ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Retinoblastoma Protein ◽  
Simian Virus 40 ◽  
Suppressor Gene ◽  
Simian Virus ◽  
T Antigen ◽  
Cellular Proteins ◽  
Adenovirus E1a ◽  
Related Family ◽  
Transforming Proteins

Even though the retinoblastoma gene is one of the best-studied tumor suppressor genes, little is known about its functional role. Like all tumor suppressor gene products, the retinoblastoma protein (pRB) is thought to inhibit some aspect of cell proliferation. It also appears to be a cellular target of several DNA tumor virus-transforming proteins, such as adenovirus E1A, human papillomavirus E7, or simian virus 40 large T antigen. To help in the analysis of pRB, we have prepared a new set of anti-human pRB monoclonal antibodies. In addition to being useful reagents for the study of human pRB, these antibodies display several unexpected properties. They can be used to distinguish different subsets of the pRBs on the basis of their phosphorylation states. Some are able to recognize pRB homologs in other species, including mice, chickens, and members of the genus Xenopus. In addition, some of these antibodies can bind directly to other cellular proteins that, like pRB, were originally identified through their association with adenovirus E1A. These immunologically cross-reactive proteins include the p107 and p300 proteins, and their recognition by antibodies raised against pRB suggests that several members of the E1A-targeted cellular proteins form a structurally and functionally related family.

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 Antibodies specific for the human retinoblastoma protein identify a family of related polypeptides.

1991 ◽  
Vol 11 (11) ◽  
pp. 5792-5799 ◽  
Author(s):  
Q J Hu ◽  
C Bautista ◽  
G M Edwards ◽  
D Defeo-Jones ◽  
R E Jones ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Retinoblastoma Protein ◽  
Simian Virus 40 ◽  
Suppressor Gene ◽  
Simian Virus ◽  
T Antigen ◽  
Cellular Proteins ◽  
Adenovirus E1a ◽  
Related Family ◽  
Transforming Proteins

Even though the retinoblastoma gene is one of the best-studied tumor suppressor genes, little is known about its functional role. Like all tumor suppressor gene products, the retinoblastoma protein (pRB) is thought to inhibit some aspect of cell proliferation. It also appears to be a cellular target of several DNA tumor virus-transforming proteins, such as adenovirus E1A, human papillomavirus E7, or simian virus 40 large T antigen. To help in the analysis of pRB, we have prepared a new set of anti-human pRB monoclonal antibodies. In addition to being useful reagents for the study of human pRB, these antibodies display several unexpected properties. They can be used to distinguish different subsets of the pRBs on the basis of their phosphorylation states. Some are able to recognize pRB homologs in other species, including mice, chickens, and members of the genus Xenopus. In addition, some of these antibodies can bind directly to other cellular proteins that, like pRB, were originally identified through their association with adenovirus E1A. These immunologically cross-reactive proteins include the p107 and p300 proteins, and their recognition by antibodies raised against pRB suggests that several members of the E1A-targeted cellular proteins form a structurally and functionally related family.

Structure and synthesis of a simian virus 40 super T-antigen.

1982 ◽  
Vol 44 (3) ◽  
pp. 963-973 ◽  
Author(s):  
M Lovett ◽  
C E Clayton ◽  
D Murphy ◽  
P W Rigby ◽  
A E Smith ◽  
...  
Keyword(s):  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen
Sign in / Sign up

Export Citation Format

Share Document