Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.5.1.18 (glutathione S-transferase)
22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cyclin E is an important regulator of cell cycle progression that together with cyclin-dependent kinase (cdk) 2 is crucial for the G1/S transition during the mammalian cell cycle. Previously, we showed that severe overexpression of cyclin E protein in tumor cells and tissues results in the appearance of lower molecular weight isoforms of cyclin E, which together with cdk2 can form a kinase complex active throughout the cell cycle. In this study, we report that one of the substrates of this constitutively active cyclin E/cdk2 complex is retinoblastoma susceptibility gene product (pRb) in populations of breast cancer cells and tissues that also overexpress p16. In these tumor cells and tissues, we show that the expression of p16 and pRb is not mutually exclusive. Overexpression of p16 in these cells results in sequestering of cdk4 and cdk6, rendering cyclin D1/cdk complexes inactive. However, pRb appears to be phosphorylated throughout the cell cycle following an initial lag, revealing a time course similar to phosphorylation of glutathione S-transferase retinoblastoma by cyclin E immunoprecipitates prepared from these synchronized cells. Hence, cyclin E kinase complexes can function redundantly and replace the loss of cyclin D-dependent kinase complexes that functionally inactivate pRb. In addition, the constitutively overexpressed cyclin E is also the predominant cyclin found in p107/E2F complexes throughout the tumor, but not the normal, cell cycle. These observations suggest that overexpression of cyclin E in tumor cells, which also overexpress p16, can bypass the cyclin D/cdk4-cdk6/p16/pRb feedback loop, providing yet another mechanism by which tumors can gain a growth advantage.
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PMID:Cyclin E, a redundant cyclin in breast cancer. 898 90

Cyclin-dependent kinase 4 (CDK4) is a key molecule in the regulation of cell cycle progression at the G1-S phase restriction point. Its activity is specifically regulated by p16 (also known as p16/CDKN2A, p16(INK4a), and MTS1), a tumor suppressor frequently altered in human cancers. A specific mutation in CDK4 codon 24 (Arginine to Cysteine) prevents p16 binding and thus inhibition by p16. This mutated CDK4 acts as a dominant oncogene and has been found in both sporadic and familial melanoma. To study the effects of other mutations in CDK4, we generated a panel of 18 CDK4 mutants using Charged-to-Alanine scanning mutagenesis, and investigated the p16-binding capacity of these mutants to identify novel sites involved in p16 binding. The mutant CDK4 proteins were generated by direct coupled transcription-translation in vitro and tested for binding to p16 using a p16-GST fusion protein. Several mutants demonstrated loss of p16 binding. In addition to the previously identified codon 24 mutants, alterations in and around codon 22, 25, 97, and 281 all showed loss of p16 binding capacity. These results indicate that several noncontiguous amino acid sequences on CDK4 are required for binding to p16, which suggests the existence of multiple sites of interaction with p16. Since p16-binding deficient CDK4 has oncogenic potential, these mutations may be present in melanomas or other human neoplasms.
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PMID:Several noncontiguous domains of CDK4 are involved in binding to the P16 tumor suppressor protein. 971 35

Human cdk (cyclin dependent kinase) inhibitor p16 was fused with glutathione S-transferase (GST) and the GST-p16 fusion protein is under the control of T7 promoter. When expressed in E. coli BL21(DE3), most products existed in the form of insoluble inclusion bodies. When co-expressed with molecular chaperones E. coli GroESL, most GST-p16 products accumulated in the soluble form with a 5-6 fold increase in solubility. When coproduced with human protein disulfide isomerase (PDI), there was no improvement in the solubility of GST-p16 fusion protein.
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PMID:Increased solubility of glutathione S-transferase-P16 (GST-p16) fusion protein by co-expression of chaperones groes and groel in Escherichia coli. 981 86

Recent evidence suggests that tumor cells may release DNA into the circulation, which is enriched in the serum and plasma, allowing detection of ras and p53 mutations and microsatellite alterations in the serum DNA of cancer patients. We examined whether aberrant DNA methylation might also be found in the serum of patients with non-small cell lung cancer. We tested 22 patients with non-small cell lung cancer using methylation-specific PCR, searching for promoter hypermethylation of the tumor suppressor gene p16, the putative metastasis suppressor gene death-associated protein kinase, the detoxification gene glutathione S-transferase P1, and the DNA repair gene O6-methylguanine-DNA-methyltransferase. Aberrant methylation of at least one of these genes was detected in 15 of 22 (68%) NSCLC tumors but not in any paired normal lung tissue. In these primary tumors with methylation, 11 of 15 (73%) samples also had abnormal methylated DNA in the matched serum samples. Moreover, none of the sera from patients with tumors not demonstrating methylation was positive. Abnormal promoter methylation in serum DNA was found in all tumor stages. Although these results need to be confirmed in larger studies and in other tumor types, detection of aberrant promoter hypermethylation of cancer-related genes in serum may be useful for cancer diagnosis or the detection of recurrence.
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PMID:Detection of aberrant promoter hypermethylation of tumor suppressor genes in serum DNA from non-small cell lung cancer patients. 989 87

Since the structures of several ankyrin-repeat proteins including the INK4 (inhibitor of cyclin-dependent kinase 4) family have been reported recently, the detailed structures and the functional roles of the loops have drawn considerable interest. This paper addresses the potential importance of the loops of ankyrin-repeat proteins in three aspects. First, the solution structure of p18INK4C was determined by NMR, and the loop structures were analyzed in detail. The loops adapt nascent antiparallel beta-sheet structures, but the positions are slightly different from those in the crystal structure. A detailed comparison between the solution structures of p16 and p18 has also been presented. The determination of the p18 solution structure made such detailed comparisons possible for the first time. Second, the [1H,15N]HSQC NMR experiment was used to probe the interactions between p18INK4C and other proteins. The results suggest that p18INK4C interacts very weakly with dna K and glutathione S-transferase via the loops. The third aspect employed site-specific mutagenesis and functional assays. Three mutants of p18 and 11 mutants of p16 were constructed to test functional importance of loops and helices. The results suggest that loop 2 is likely to be part of the recognition surface of p18INK4C or p16INK4A for CDK4, and they provide quantitative functional contributions of specific residues. Overall, our results enhance understanding of the structural and functional roles of the loops in INK4 tumor suppressors in particular and in ankyrin-repeat proteins in general.
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PMID:Tumor suppressor INK4: determination of the solution structure of p18INK4C and demonstration of the functional significance of loops in p18INK4C and p16INK4A. 1007 45

Hypermethylation in cancer often occurs in CpG islands that span the promoter regions of tumor suppressor genes. However, it is not clear if hypermethylation is limited to single target genes or if multiple genes are simultaneously methylated. To understand the extent of aberrant de novo methylation, we have analyzed the methylation pattern of a number of tumor-related genes in leukemia from the same cohort of patients. We used bisulfite genomic sequencing to characterize the methylation pattern of the CpG islands associated with the calcitonin, estrogen receptor, E-cadherin, p15, p16, Rb, GST-Pi, and HIC1 genes in the bone marrow from 9 normal and 20 patients with acute myeloid leukaemia (AML). All of the normal control samples were essentially unmethylated for each of the eight tumor-related genes studied. In contrast, 19 of 20 (95%) of the AML patients had an abnormal methylation pattern in at least one gene, and 15 of 20 (75%) had abnormal methylation patterns in two or more of the target genes. We conclude that there is a general deregulation of CpG island methylation in leukemia and that hypermethylation is not limited to single genes, but a number of genes are methylated concurrently. Moreover, the subset of genes that are commonly methylated in leukemia appear to be cancer type specific.
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PMID:Concurrent DNA hypermethylation of multiple genes in acute myeloid leukemia. 1044 89

Promoter hypermethylation is an important pathway for repression of gene transcription in cancer cells. We analyzed aberrant DNA methylation at four genes in primary tumors from 95 head and neck cancer patients and then used the presence of this methylation as a marker for cancer cell detection in serum DNA. These four genes were tested by methylation-specific PCR and included: p16 (CDKN2A), O6-methylguanine-DNA-methyltransferase, glutathione S-transferase P1, and death-associated protein kinase (DAP-kinase). Fifty-five % (52 of 95) of the primary tumors displayed promoter hypermethylation in at least one of the genes studied: 27% (26/95) at p16, 33% (31 of 95) at O6-methylguanine-DNA-methyltransferase; and 18% (17 of 92) at DAP-kinase. No promoter hypermethylation was observed at the glutathione S-transferase P1 gene promoter. We detected a statistically significant correlation between the presence of DAP-kinase gene promoter hypermethylation and lymph node involvement (P = 0.014) and advanced disease stage (P = 0.016). In 50 patients with paired serum available for epigenetic analysis, the same methylation pattern was detected in the corresponding serum DNA of 21 (42%) cases. Among the patients with methylated serum DNA, 5 developed distant metastasis compared with the occurrence of metastasis in only 1 patient negative for serum promoter hypermethylation (P = 0.056). Promoter hypermethylation of key genes in critical pathways is common in head and neck cancer and represents a promising serum marker for monitoring affected patients.
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PMID:Gene promoter hypermethylation in tumors and serum of head and neck cancer patients. 1070 1

To clarify the sequential changes in pRB and p16 during different stages of hepatocarcinogenesis such as fibrosis, cirrhosis, hepatocellular adenoma (HCA), and hepatocellular carcinoma (HCC), male Fischer 344 rats were singly injected with diethylnitrosamine (DEN), immediately followed with phenobarbital for 1 wk and then thioacetamide (TAA) for 39 wk in drinking water. Rats were killed at 9, 20, 30, and 40 wk after DEN initiation and changes of pRB level, p16 gene hypermethylation, and in vivo gankyrin expression were examined. Histologic examination showed stepwise appearances of fibrosis, cirrhosis, HCA, and HCC at weeks 9, 20, 30, and 40, respectively. Hypermethylation of p16 exon 1 was not found until HCA but appeared in 50% of the rats with HCC accompanied by complete loss of its mRNA expression. The amount of glutathione S-transferase--gankyrin bound to pRB and pRB degradation in the liver depended on the concentration of gankyrin and incubation time. Gankyrin expression preceded pRB degradation in liver cirrhosis. In conclusion, gankyrin expression induced in liver fibrosis accelerated the degradation of pRB during liver cirrhosis, and inactivation of p16 exon 1 by DNA hypermethylation occurred during the progression of tumor cells to poorly differentiated HCC. Inactivation of pRB and/or p16 resulted in complete loss of regulation in the cell-division cycle during early and late stages, respectively, of hepatocarcinogenesis. Mol. Carcinog. 30:138--150, 2001.
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PMID:Sequential changes in hepatocarcinogenesis induced by diethylnitrosamine plus thioacetamide in Fischer 344 rats: induction of gankyrin expression in liver fibrosis, pRB degradation in cirrhosis, and methylation of p16(INK4A) exon 1 in hepatocellular carcinoma. 1130 74

Promoter hypermethylation plays an important role in the inactivation of tumor suppressor genes during tumorigenesis. Recent data suggest that such epigenetic abnormality may occur very early in lung carcinogenesis. To determine the extent of promoter hypermethylation in early lung tumorigenesis, we analyzed promoter methylation status of the p16, death-associated protein kinase (DAPK) and glutathione S-transferase P1 (GSTP1) genes using methylation-specific PCR in bronchial brush samples obtained from 100 former smokers enrolled in a chemoprevention clinical trial. We found that 17% of the samples showed methylation for p16 and 17% the same for DAPK, whereas only 6% of the samples displayed methylation for GSTP1. A total of 32% of the samples had methylation in at least one of the three genes tested, and 8% of the samples had methylation in two genes. The methylation status of p16 was correlated with that of DAPK (P = 0.04, Fisher's exact test). p16 methylation was higher in former smokers with a history of previous cancer than in former smokers without a history of cancer (P = 0.04, Fisher's exact test), and methylation of DAPK was detected more frequently in older patients than it was in younger patients (P = 0.01, Wilcoxon rank-sum test). Surprisingly, no correlation was found between methylation in any of these genes and the smoking characteristics of the individuals analyzed (packs per day, pack-years, smoking years, quitting years). The precise meaning of methylated genes in the bronchial brush samples of former smokers must be sought by means of careful follow-up of these individuals.
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PMID:Aberrant promoter methylation of multiple genes in bronchial brush samples from former cigarette smokers. 1180 77

Mechanisms for bladder carcinogenesis and the development of recurrentbladder cancer remain unclear. Aberrant methylation of the 5' CpG island is thought to play an important role in the inactivation of the tumor suppressor genes in cancer. To study whether specific or bulk hypermethylation predicts intrabladder recurrence, we determined the frequency of aberrant promoter hypermethylation of seven genes, hMLH1, O(6)-methylguanine-DNA-methyltransferase (MGMT), p16, Von Hippel-Lindau (VHL), death-associated protein kinase (DAP-kinase), glutathione S-transferase P1 (GST-P1) and E-cadherin in 55 superficial bladder cancers and 5 normal urothelial epithelia by methylation-specific PCR (MSP). These patients of superficial bladder cancer had been followed prospectively by cystoscopy. Simultaneous hypermethylation of three genes or more among the seven genes was observed in 2 (7%) of 30 patients in the nonrecurrence group and 7 (28%) of 25 patients in the recurrence group. There was a significant concordance between the number of methylated genes and the development of recurrence (P = 0.012). In particular, the recurrence rate for 24 months was 88% for hypermethylation of DAP-kinase and 28% for nonmethylation of DAP-kinase. Hypermethylation of DAP-kinase is, therefore, a strong indicator of the superficial bladder cancer associated with a high recurrence rate (P < 0.001; hazards ratio, 7.01). Our results suggest that hypermethylation of DAP-kinase might be a useful prognostic marker for disease recurrence in superficial bladder cancers.
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PMID:The association of death-associated protein kinase hypermethylation with early recurrence in superficial bladder cancers. 1212 40


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