Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In response to DNA damage, the transcriptional activity of p53 rises. This has been thought to be due to an increase in the level of p53 protein. By comparing the p53 protein level and its ability to transactivate target genes Waf1/Cip1 and mdm2 in both T22 and NIH3T3 cells irradiated with u.v., a discordance between the p53 protein level and its transcriptional activity was observed. When the cells were irradiated with 10 J/m2 of u.v., there was a substantial increase in expression of Waf1/ Cip1 and mdm2. However, little increase in Waf1/Cip1 and mdm2 expression was observed in T22 and NIH3T3 cells 8 or 9 h after exposure to 50 J/m2 of u.v., although the p53 protein level accumulated to its highest level under these conditions. Interestingly, a significant increase in Waf1/Cip1 expression was seen 24 h after irradiation in NIH3T3 cells, indicating that the inhibition of p53 transcriptional activity is reversible. Discordance between the transcriptional activity of p53 and its protein level was further studied using a cell line expressing the p53 reporter plasmid RGC delta fosLacZ. Using double immunofluorescence staining, the coexpression of p53 and beta-galactosidase from the reporter plasmid in the same cells was investigated. The observed lack of correlation between the elevated p53 and beta-galactosidase and expression in u.v. irradiated cells strongly indicates that the ability of p53 to transactivate its target genes is not simply correlated to its protein level. The results indicate that the transcriptional activity of p53 may be negatively regulated.
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PMID:Discordance between accumulated p53 protein level and its transcriptional activity in response to u.v. radiation. 871 Mar 81

Since transcriptional activation of genes downregulating cell proliferation mediates the tumor suppressor activity of p53, induction of p53 targets was assumed to adequately reflect the state of p53-dependent pathways. To estimate the p53 activity in cultured cells, self-inactivating retrovirus constructs pSIP-ConA-GFP and pSIP-ConA-LacZ were obtained to express the GFP or beta-galactosidase reporter gene under the control of a promoter containing p53-responsive elements. The advantages of these constructs were efficient delivery, comparable expression in different cells of a culture, and, consequently, the possibility of quantitating the p53 activity induced by various agents. With pSIP-ConA-LacZ, p53 activation in response to 12 chemotherapeutic agents was analyzed in human carcinoma cell line HCT116 and its derivatives HCT116/mdm2 and HCT116ARF, which expressed genes affecting the p53 activity. The analysis was also carried out with human cell lines HEF, WI-38, U2OS, and HT1080 originating from connective tissue. The construct proved suitable for detecting fine differences in p53 activation induced by various stress factors. The constructs were proposed for generating reporter cell lines from various cultures in order to identify the genetic or chemical factors that modulate the p53 activity and may be employed in new antitumor drugs.
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PMID:[Construction of a reporter system for fine quantitative assessment of activity of p53 protein in cultured cells]. 1471 96

Mutation of the p53 gene is a common event during tumor pathogenesis. Other mechanisms, such as mdm2 amplification, provide alternative routes through which dysfunction of the p53 pathway is promoted. Here, we address the hypothesis that elevated expression of pim oncogenes might suppress p53 by regulating Mdm2. At a physiological level, we show that endogenous Pim-1 and Pim-2 interact with endogenous Mdm2. Additionally, the Pim kinases phosphorylate Mdm2 in vitro and in cultured cells at Ser(166) and Ser(186), two previously identified targets of other signaling pathways, including Akt. Surprisingly, at high levels of Pim expression, as would occur in tumors, active, but not inactive, Pim-1 or Pim-2 blocks the degradation of both p53 and Mdm2 in a manner that is independent of Mdm2 phosphorylation, leading to increased p53 levels and, proportionately, p53-dependent transactivation. Additionally, Pim-1 induces endogenous ARF, p53, Mdm2, and p21 in primary murine embryo fibroblasts and stimulates senescence-associated beta-galactosidase levels, consistent with the induction of senescence. Immunohistochemical analysis of a cohort of 33 human mantle cell lymphomas shows that elevated expression of Pim-1 occurs in 42% of cases, with elevated Pim-2 occurring in 9% of cases, all of which also express Pim-1. Notably, elevated Pim-1 correlates with elevated Mdm2 in MCL with a p value of 0.003. Taken together, our data are consistent with the idea that Pim normally interacts with the p53 pathway but, when expressed at pathological levels, behaves as a classic dominant oncogene that stimulates a protective response through induction of the p53 pathway.
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PMID:Elevated levels of oncogenic protein kinase Pim-1 induce the p53 pathway in cultured cells and correlate with increased Mdm2 in mantle cell lymphoma. 1846 33