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

---

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

BRCA1, a familial breast and ovarian cancer susceptibility gene encodes nuclear phosphoproteins that function as tumor suppressors in human breast cancer cells. Previously, we have shown that overexpression of a BRCA1 splice variant BRCA1a accelerates apoptosis in human breast cancer cells. In an attempt to determine whether the subcellular localization of BRCA1 is cell cycle regulated, we have studied the subcellular distribution of BRCA1 in asynchronous and growth arrested normal, breast and ovarian cancer cells using different BRCA1 antibodies by immunofluorescence and immunohistochemical staining. Upon serum starvation of NIH3T3, some breast and ovarian cancer cells, most of the BRCA1 protein redistributed to the nucleus revealing a new type of regulation that may modulate the activity of BRCA1 gene. We have also characterized two new variant BRCA1 proteins (BRCA1a/p110 and BRCA1b/ p100) which are phosphoproteins containing phosphotyrosine. Immunofluorescence and Western blotting analysis indicate cytoplasmic and nuclear localization of BRCA1a and BRCA1b proteins. To elucidate the biological function of BRCA1, we created a bacterial fusion protein of glutathione-transferase (GST) and BRCA1 zinc finger domain and detected two cellular proteins with molecular weights of approximately 32 and 65 kD, one of which contains phosphotyrosine designated p32 and p65 BRCA1 interacting proteins (BIP) that specifically interact with BRCA1. Western blot analysis of BIP with cyclins/CDKs and E2F antisera indicated association with cdc2, cdk2, cdk4, cyclin B, cyclin D, cyclin A and E2F-4 but not with cdk3, cdk5, cdk6, E2F-1, E2F-2, E2F-3, E2F-5 and cyclin E. Furthermore, we have also demonstrated a direct interaction of in vitro translated BRCA1a and BRCA1b proteins with recombinant cyclin A, cyclin B1, cyclin D1, cdc2, cdk2 and E2F fusion proteins in vitro. Taken together these results seem to suggest that BRCA1 could be an important negative regulator of cell cycle that functions through interaction with E2F transcriptional factors and phosphorylation by cyclins/cdk complexes with the zinc ring finger functioning as a major protein-protein interaction domain. If the interactions we observe in vitro is also seen in vivo then it may be possible that lack or impaired binding of the disrupted BRCA1 proteins to E2F, cyclins/CDKs in patients with mutations in the zinc finger domain could deprive the cell of an important mechanism for braking cell proliferation leading to the development of breast and ovarian cancers.
...
PMID:BRCA1 proteins are transported to the nucleus in the absence of serum and splice variants BRCA1a, BRCA1b are tyrosine phosphoproteins that associate with E2F, cyclins and cyclin dependent kinases. 924 50

Active transport of proteins into the nucleus is mediated by interaction between the classical nuclear localization signals (NLSs) of the targeted proteins and the NLS receptor (importin) complex. This nuclear transport system is highly regulated and conserved in eukaryotes and is essential for cell survival. Using a fragment of BRCA1 containing the two NLS motifs as a bait for yeast two-hybrid screening, we have isolated four clones, one of which is importin alpha. Here we characterize one of the other clones identified, BRAP2, which is a novel gene and expressed as a 2-kilobase mRNA in human mammary epithelial cells and some but not all tissues of mice. The isolated full-length cDNA encodes a novel protein containing 600 amino acid residues with pI 6.04. Characteristic motifs of C2H2 zinc fingers and leucine heptad repeats are present in the middle and C-terminal regions of the protein, respectively. BRAP2 also shares significant homology with a hypothetical protein from yeast Saccharomyces cerevisiae, especially in the zinc finger region. Antibodies prepared against the C-terminal region of BRAP2 fused to glutathione S-transferase specifically recognize a cellular protein with a molecular size of 68 kDa, consistent with the size of the in vitro translated protein. Cellular BRAP2 is mainly cytoplasmic and binds to the NLS motifs of BRCA1 with similar specificity to that of importin alpha in both two-hybrid assays in yeast and glutathione S-transferase pull-down assays in vitro. Other motifs such as the SV40 large T antigen NLS motif and the bipartite NLS motif found in mitosin are also recognized by BRAP2. Similarly, the yeast homolog of BRAP2 also binds to these NLS motifs in vitro. These results imply that BRAP2 may function as a cytoplasmic retention protein and play a role in regulating transport of nuclear proteins.
...
PMID:Identification of a novel cytoplasmic protein that specifically binds to nuclear localization signal motifs. 949 40

The tumor suppressor gene BRCA1, is a nuclear phosphoprotein which associates with RNA polymerase II holoenzyme. CBP is a component of the holoenzyme. Previously, we have characterized two new BRCA1 splice variants BRCA1a/p110 and BRCA1b/p100. In the present study, the carboxy-terminal domain of transcription factor CBP interacts both in vivo and in vitro with full length BRCA1a and BRCA1b proteins as demonstrated by mammalian two- hybrid assays, co-immunoprecipitation/western blot studies, GST binding assays and histone acetyl transferase (HAT) assays of BRCA1 immunoprecipitates from human breast cancer cells. Our results suggest that one of the mechanisms by which BRCA1 proteins function is through recruitment of CBP associated HAT/FAT (transcription factor acetyl-transferase) activity for acetylation of either themselves or general transcription factors or both to specific promoters resulting in transcriptional activation.
...
PMID:BRCA1 splice variants BRCA1a and BRCA1b associate with CBP co-activator. 953 57

The breast cancer susceptibility gene BRCA1 encodes a nuclear phosphoprotein that acts as a tumor suppressor. Phosphorylation of BRCA1 has been implicated in altering its function, however, the pathway(s) that leads to the phosphorylation of BRCA1 has not been described. Here, a signaling pathway by which heregulin induces cell cycle-independent phosphorylation of BRCA1 was delineated. We showed that heregulin stimulation induced the phosphorylation of BRCA1 and concomitant activation of the serine/threonine kinase AKT in T47D human breast cancer cells. Heregulin-induced phosphorylation of BRCA1 was abrogated by phosphatidylinositol 3-kinase (PI3K) inhibitors and by a dominant-negative AKT. In the absence of heregulin, the ectopic expression of the constitutively active p110 subunit of PI3K was sufficient to induce BRCA1 phosphorylation. Furthermore, the purified glutathione S-transferase/AKT kinase phosphorylated BRCA1 in vitro. We have also shown that the phosphorylation of BRCA1 by AKT occurs on the residue Thr-509, which is located in the nuclear localization signal. These results reveal a novel signaling pathway that links extracellular signals to the phosphorylation of BRCA1 in breast cancer cells.
...
PMID:Heregulin induces phosphorylation of BRCA1 through phosphatidylinositol 3-Kinase/AKT in breast cancer cells. 1054 66

The existence of genetic alterations affecting genes involved in cellular proliferation and death, such as TP53 and K-ras, is one of the most common features of tumour cells. Recently, gene inactivation by promoter hypermethylation has been demonstrated. Methylation is the main epigenetic modification in mammals and abnormal methylation of the CpG islands located in the promoter region of the genes leads to transcriptional silencing. Examples include the p16INK4a, p15INK4B, p14ARF, Von Hippel-Lindau (VHL), the oestrogen and progesterone receptors, E-cadherin, death associated protein (DAP) kinase and the first tumour suppressor gene described, retinoblastoma (Rb) gene. In most cases, methylation involves loss of expression, absence of a coding mutation and restoration of transcription by the use of demethylating agents. However, is there a linkage between genetic and epigenetic alterations? Our results show one side of this puzzle demonstrating that epigenetic lesions drive genetic lesions in cancer. Four specific epigenetic lesions, promoter hypermethylation of the DNA mismatch repair gene hMLH1, the DNA alkyl-repair gene O(6)-methylguanine-DNA methyltransferase (MGMT), the detoxifier glutathione S-transferase P1 (GSTP1) and the familial breast cancer gene BRCA1 may lead to four specific genetic lesions, microsatellite instability, G to A transitions, steroid-related adducts and double-strand breaks in DNA. This is probably only the beginning of an extensive list of epigenetic events that change and make the genetic environment of the transformed cell unstable.
...
PMID:Epigenetic lesions causing genetic lesions in human cancer: promoter hypermethylation of DNA repair genes. 1109 2

Elk-1, a c-Fos protooncogene regulator, which belongs to the ETS-domain family of transcriptional factors, plays an important role in the induction of immediate early gene expression in response to a variety of extracellular signals. In this study, we demonstrate for the first time the in vitro and in vivo interaction of Elk-1 with BRCA1 splice variants BRCA1a and BRCA1b using GST-pull down assays, co-imunoprecipitations/Western blot analysis of cell extracts from breast cancer cells and mammalian two-hybrid assays. We have localized the BRCA1 interaction domain of Elk-1 protein to the conserved ETS domain, a motif involved in DNA binding and protein-protein interactions. We also observed binding of BRCA1 proteins to other ETS-domain transcription factors SAP1, ETS-1, ERG-2 and Fli-1 but not to Elk-1 splice variant DeltaElk-1 and c-Fos protooncogene. Both BRCA1a and BRCA1b splice variants function as growth suppressors of human breast cancer cells. Interestingly, our studies reveal that although both Elk-1 and SAP-1 are highly homologous members of a subfamily of ETS domain proteins called ternary complex factors, it is only Elk-1 but not SAP-1 that can augment the growth suppressive function of BRCA1a/1b proteins in breast cancer cells. Thus Elk-1 could be a potential downstream target of BRCA1 in its growth control pathway. Furthermore, we have observed inhibition of c-Fos promoter activity in BRCA1a transfected stable breast cancer cells and over expression of BRCA1a/1b attenuates MEK-induced SRE activation in vivo. These results demonstrate for the first time a link between the growth suppressive function of BRCA1a/1b proteins and signal transduction pathway involving Elk-1 protein. All these results taken together suggest that one of the mechanisms by which BRCA1a/1b proteins function as growth/tumor suppressors is through inhibition of the expression of Elk-1 target genes like c-Fos.
...
PMID:c-Fos oncogene regulator Elk-1 interacts with BRCA1 splice variants BRCA1a/1b and enhances BRCA1a/1b-mediated growth suppression in breast cancer cells. 1131 79

Numerous reports have revealed that the tumor suppressor BRCA1 may play an important role in DNA damage repair. BRCA1 is expressed and phosphorylated during cell cycle progression and after DNA damage. BRCA1 is hypophosphorylated in G0-G1 and probably during mitosis as well. Kinases known to phosphorylate BRCA1 include cyclin-dependent kinase 2, as well as ataxia telangiectasia-mutated (ATM) and ATM and Rad3-related kinase (ATR), which function in G2 checkpoint control. However, protein phosphatases responsible for dephosphorylation of BRCA1 had yet to be identified. hCds1, which acts downstream of ATM, also phosphorylates a BRCA1 fragment containing amino acids 759-1064 [BRCA1 fragment 4 (BF4)]. We have used a GST-BF4 protein phosphorylated by hCds1 [glutathione S-transferase (GST)-BF4-P] as a substrate to identify potential phosphatases responsible for BRCA1 dephosphorylation. Data presented here show that both recombinant protein phosphatase 1 alpha (PP1alpha) catalytic subunit and endogenous PP1alpha dephosphorylate GST-BF4-P. Inhibitor 2 abolishes this activity. Overexpression of PP1alpha partially inhibits hyperphosphorylation of BRCA1 after ionizing radiation, indicating that PP1alpha dephosphorylates BRCA1 in vivo. BRCA1 and PP1alpha reciprocally coimmunoprecipitate, and a glutathione S-transferase pull-down assay shows that PP1alpha catalytic subunit associates directly with the BF4 region of BRCA1. In addition, BRCA1 inhibits PP1alpha activity. Therefore, BRCA1 is both a substrate and a regulator of PP1alpha. The interaction between BRCA1 and PP1alpha thus may play a role in DNA damage repair and cell cycle progression.
...
PMID:Regulation of BRCA1 phosphorylation by interaction with protein phosphatase 1alpha. 1243 14

BRCA1 is a tumor suppressor gene mutated in cases of hereditary breast and ovarian cancer. BRCA1 protein is involved in apoptosis and growth/tumor suppression. In this study, we present evidence that p65/RelA, one of the two subunits of the transcription factor NF-kappaB, binds to the BRCA1 protein. Treatment of 293T cells with the cytokine tumor necrosis factor-alpha induces an interaction between endogenous p65/RelA and BRCA1. GST-protein affinity assay experiments reveal that the Rel homology domain of the p65/RelA subunit of NF-kappaB interacts with multiple sites within the N-terminal region of BRCA1. Transient transfection of BRCA1 significantly enhances the ability of the tumor necrosis factor-alpha or interleukin-1beta to activate transcription from the promoters of NF-kappaB target genes. Mutation of the NF-kappaB-binding sites in the NF-kappaB reporter blocks the effect of BRCA1 on transcription. Also the ability of BRCA1 to activate NF-kappaB target genes is inhibited by a super-stable inhibitor of NF-kappaB and by the chemical inhibitor SN-50. These data indicate that BRCA1 acts as a co-activator with NF-kappaB. In addition, we show that cells infected with an adenovirus expressing BRCA1 up-regulate the endogenous expression of NF-kappaB target genes Fas and interferon-beta. Together, this information suggests that BRCA1 may play a role in cell life-death decisions following cell stress by modulation of the activity of NF-kappaB.
...
PMID:BRCA1 augments transcription by the NF-kappaB transcription factor by binding to the Rel domain of the p65/RelA subunit. 1270 Feb 28

The insulin-like growth factor-I receptor (IGF-IR) plays a critical role in breast tumorigenesis and is overexpressed in most primary tumors. BRCA1 is a transcription factor involved in numerous cellular processes, including DNA damage repair, cell growth, and apoptosis. Consistent with its tumor suppressor role, we demonstrated that BRCA1 repressed the activity of co-transfected IGF-IR promoter reporter constructs in a number of breast cancer-derived cell lines. Results of electrophoretic mobility shift assay showed that BRCA1 did not exhibit any specific binding to the IGF-IR promoter, although it prevented binding of Sp1. Co-immunoprecipitation experiments demonstrated that BRCA1 action was associated with specific interaction with Sp1 protein. Furthermore, using a series of glutathione S-transferase-tagged BRCA1 fragments, we mapped the Sp1-binding domain to a segment located between aa 260 and 802. In summary, our data suggest that the IGF-IR gene is a novel downstream target for BRCA1 action.
...
PMID:BRCA1-Sp1 interactions in transcriptional regulation of the IGF-IR gene. 1270 36

Fanconi anaemia (FA) is a cancer-prone genetic disorder that is characterised by cytogenetic instability and redox abnormalities. Although rare subtypes of FA (B, D1 and D2) have been implicated in DNA repair through links with BRCA1 and BRCA2, such a role has yet to be demonstrated for gene products of the common subtypes. Instead, these products have been strongly implicated in xenobiotic metabolism and redox homeostasis through interactions of FANCC with cytochrome P-450 reductase and with glutathione S-transferase, and of FANCG with cytochrome P-450 2E1, as well as redox-dependent signalling through an interaction between FANCA and Akt kinase. We hypothesise that FA proteins act directly (via FANCC and FANCG) and indirectly (via FANCA, BRCA2 and FANCD2) with the machinery of cellular defence to modulate oxidative stress. The latter interactions may co-ordinate the link between the response to DNA damage and oxidative stress parameters (3, 6-12).
...
PMID:Fanconi anaemia proteins: major roles in cell protection against oxidative damage. 1276 48


1 2 3 Next >>

---