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S Maheswaran

Publications and source records attributed to S Maheswaran.

26 records · Page 2Linked to original sources
PubMed1995

The WT1 gene product stabilizes p53 and inhibits p53-mediated apoptosis.

The Wilms' tumor-suppressor gene product WT1 coimmunoprecipitates with p53 from baby rat kidney (BRK) cells and Wilms' tumor specimens, and expression of WT1 in BRK cells is associated with increased levels of endogenous wild-type p53 protein. To study the effect of WT1 on p53 function, we cotransfected expression constructs into Saos-2 cells, an osteosarcoma cell line without endogenous expression of either gene. Expression of WT1 resulted in increased steady-state levels of p53, attributable to a prolongation in protein half-life, and associated with protection against papillomavirus E6-mediated degradation of p53. This effect mapped to zinc fingers 1 and 2 of WT1 and was not observed with the closely related EGR1 protein. The stabilized p53 demonstrated enhanced binding to its target DNA sequence and increased trans-activation of a promoter containing this RGC site, but reduced transcriptional repression of a TATA-containing promoter lacking this site. Expression of WT1 inhibited p53-mediated apoptosis triggered by UV irradiation or by expression of temperature-sensitive p53 in the wild-type conformation, but did not affect p53-mediated cell cycle arrest. We conclude that WT1 protein can stabilize p53, modulate its trans-activational properties, and inhibit its ability to induce apoptosis. This effect may contribute to the elevated levels of wild-type p53 protein that are observed in Wilms' tumors.

Animals↗
PubMed1994

Intracellular association of the protein product of the c-myc oncogene with the TATA-binding protein.

The c-myc proto-oncogene encodes nuclear phosphoproteins that bind DNA in a sequence-specific fashion and appear to function as transcriptional activators. Here we demonstrate that a 40-kDa nuclear protein coimmunoprecipitated with c-Myc specifically when nuclear proteins, extracted from nuclei of exponentially growing murine B-lymphoma WEHI 231 cells by using procedures for preparation of trans-acting factors, were reacted with anti-c-Myc antibodies made against different regions of the c-Myc protein. In contrast, preparation of nuclear lysates under denaturing conditions significantly reduced this coprecipitation. Upon incubation of WEHI 231 cells with the reversible chemical cross-linking agent dithiobis(succinimidyl propionate), the 40-kDa protein could be cross-linked to c-Myc protein intracellularly. Identification of the 40-kDa protein as the TATA-binding protein (TBP) of the TFIID transcription initiation complex was made by comigration and V-8 protease mapping, which yielded identical peptide fragments upon digestion of the 40-kDa protein and material immunoprecipitated with an anti-TBP specific antibody. Furthermore, in vitro-translated TBP bound to the amino-terminal portion of c-Myc. Column chromatography of cross-linked nuclear proteins showed TBP to be in a large-molecular-weight complex with c-Myc, consistent with a transcription initiation complex. These results indicate that intracellularly, c-Myc interacts with TBP, suggesting a mechanism of interaction of this oncoprotein with the basal transcription machinery.

Animals↗
PubMed1993

WT1-mediated growth suppression of Wilms tumor cells expressing a WT1 splicing variant.

A human Wilms tumor cell line (RM1) was developed to test the tumor suppressor activity of WT1, a zinc finger transcription factor that is expressed in the developing human kidney and is mutationally inactivated in a subset of Wilms tumors. Transfection of each of four wild-type WT1 isoforms suppressed the growth of RM1 cells. The endogenous WT1 transcript in these cells was devoid of exon 2 sequences, a splicing alteration that was also detected in varying amounts in all Wilms tumors tested but not in normal kidney. Production of this abnormal transcript, which encodes a functionally altered protein, may represent a distinct mechanism for inactivating WT1 in Wilms tumors.

Alternative Splicing↗
PubMed1993

Physical and functional interaction between WT1 and p53 proteins.

WT1 is a tumor-suppressor gene expressed in the developing kidney, whose inactivation leads to the development of Wilms tumor, a pediatric kidney cancer. WT1 encodes a transcription factor which binds to the EGR1 consensus sequence, mediating transcriptional repression. We now demonstrate that p53, the product of a tumor-suppressor gene with ubiquitous expression, physically associates with WT1 in transfected cells. The interaction between WT1 and p53 modulates their ability to transactivate their respective targets. In the absence of p53, WT1 acts as a potent transcriptional activator of the early growth response gene 1 (EGR1) site, rather than a transcriptional repressor. In contrast, WT1 exerts a cooperative effect on p53, enhancing its ability to transactivate the muscle creatine kinase promoter.

Animals↗
PubMed1993

The Wilms tumour gene WT1 is expressed in murine mesoderm-derived tissues and mutated in a human mesothelioma.

The tumour suppressor gene WT1 encodes a transcription factor expressed in tissues of the genito-urinary system. Inactivation of this gene is associated with the development of Wilms tumour a pediatric kidney cancer. We show that WT1 is also expressed at high levels in many supportive structures of mesodermal origin in the mouse. We also describe a case of adult human mesothelioma, a tumour derived from the peritoneal lining, that contains a homozygous point mutation within WT1. This mutation, within the putative transactivation domain, converts the protein from a transcriptional repressor of its target sequence to a transcriptional activator. The role of WT1 in normal development thus extends to diverse structures derived from embryonic mesoderm and disruption of WT1 function contributes to the onset of adult, as well as pediatric, tumours.

Adult↗
PubMed1992

Impact of do-not-resuscitate legislation on the use of cardiopulmonary resuscitation in three teaching hospitals.

Under New York State's unique do-not-resuscitate law, patients admitted to a hospital are assumed to consent to cardiopulmonary resuscitation unless a do-not-resuscitate order has been written in accordance with specific stipulations. This study was undertaken to determine if the law would significantly change the use of cardiopulmonary resuscitation. The charts of 952 patients who died on the medical services of Bellevue, New York University, and New York Veterans hospitals during the 12-month periods before and after the law went into effect were reviewed. The proportion of patients undergoing cardiopulmonary resuscitation was determined. To take into account the effects of potential confounders (ie, hospital, sex, race or ethnic group, age, diagnosis), a multiple logistic regression analysis was performed. The relative risk for cardiopulmonary resuscitation was found to be 0.81, (95% confidence interval: 0.59-1.10) after the law as compared with before, which was not statistically significant. Although patients with chronic or potentially reversible illness were much more likely than those with hopeless illness to undergo cardiopulmonary resuscitation (relative risk of 7.08 [3.23-15.54] and 12.89 [8.71-19.07], respectively), the data failed to show that the law had an impact on the use of cardiopulmonary resuscitation in any of the disease categories. Total use of formal do-not-resuscitate orders increased from 32.7% to 83.9% (p less than .0001), although at Bellevue, where documentation was high before the law, no further increase occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Changes in phosphorylation of myc oncogene and RB antioncogene protein products during growth arrest of the murine lymphoma WEHI 231 cell line.

The expression of the protein products of the c-myc oncogene and retinoblastoma susceptibility gene (RB) was investigated during either goat anti-mouse immunoglobulin (GaMIg)- or phorbol ester (TPA)-induced growth arrest of the murine B-lymphoma cell line WEHI 231. Previously we have demonstrated that c-myc mRNA levels increase within 1-2 h of treatment, return to control levels by 4 h, and decline below these values by 24 h of treatment. Here we demonstrate that the level of c-myc protein synthesis and mRNA change in parallel. The predominant c-myc protein expressed during the time course is the one initiated at the AUG codon (P2). The myc protein synthesized following 1-2 h of anti-immunoglobulin or TPA treatment migrates more slowly in a polyacrylamide gel as a result of increased phosphorylation. This hyperphosphorylation was no longer detectable by 4-6 h of treatment. Furthermore, the hyperphosphorylated myc protein appears to be more readily extractable with salt than the hypophosphorylated form. The product of the RB gene is present in multiple phosphorylation states in exponentially growing WEHI 231 cells. By 8 h of GaMIg or TPA treatment, a hypophosphorylated form begins to be detectable and significant levels were seen by 15 h. Thus post-translational control of both c-myc and RB expression occurs during the growth arrest of WEHI 231 cells. These changes in phosphorylation may play a role in mediating the cessation of proliferation of these cells.

Animals↗