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:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Epstein-Barr nuclear antigen (EBNA)-3 and EBNA-4 proteins are thought to act as transcriptional transactivators. The yeast two-hybrid system and coimmunoprecipitation were used to demonstrate that EBNA-3 and -4 associate with the DNA-binding protein RBP-2N, an isoform of RBP-J kappa. A comparison between EBNA-3, EBNA-4, and EBNA-6 binding to RBP-2N indicated that EBNA-3 enhanced beta-galactosidase activity 4-fold more than EBNA-6 and 30-fold more than EBNA-4. Assay of RBP-2N deletion mutants demonstrated that EBNA-3 binds to regions of RBP-2N which are distinct from those to which EBNA-2 and -6 interact, whereas EBNA-4 binds to the same region of RBP-2N as EBNA-2 and -6 (amino acids 159-331 of RBP-2N). Interaction of both A- and B-type EBNA-3 with RBP-2N was also demonstrated by immunoprecipitation. RT-PCR analysis of a panel of B cell lymphomas and lymphoblastoid cell lines demonstrated that higher levels of RBP-2N were expressed, in comparison to RBP-J kappa, indicating that RBP-2N is a major isoform expressed in B cells. These results suggest that all the EBNA-3 family proteins lead to transcriptional regulation via interaction with RBP-2N.
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PMID:Epstein-Barr nuclear antigen-3 and -4 interact with RBP-2N, a major isoform of RBP-J kappa in B lymphocytes. 895 54

TrwA protein was purified from an overproducing Escherichia coli strain and characterized as a 53 kDa tetrameric DNA-binding protein. Gel shift assays showed that TrwA bound specifically to the oriT sequence of plasmid R388. DNAse I footprinting analysis defined two DNA regions within oriT (sites A and B) that were protected by TrwA. At low TrwA concentrations only region A was protected (K(D) = 4 x 10(-8) M) while region B required higher TrwA concentrations (K(D) = 4 x 10(-7) M). As a result of its binding to oriT, TrwA was found to perform two biochemical activities related to its role in R388 conjugation. First, TrwA binding to oriT resulted in transcriptional repression of the trwABC operon as indicated by its effect on the beta-galactosidase activity of transcriptional fusions in trwB and trwC, and by direct measurement of the trwA mRNA levels by hybridization. This result was further confirmed by the fact that TrwA overexpression resulted in lowered conjugation frequencies. Second, TrwA enhanced the relaxation activity of TrwC in vitro. This effect was correlated to a 10(5)-fold increase in the frequency of conjugation in vivo and was shown to be independent of the regulation of transcription. Thus, TrwA shows functional similarities to protein TraY of F-like plasmids, that could be correlated to a structural similarity in their DNA-binding motifs.
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PMID:oriT-processing and regulatory roles of TrwA protein in plasmid R388 conjugation. 923 21

DtxR is a dimeric, sequence-specific, DNA-binding protein that functions as an iron-dependent, negative global regulator in Corynebacterium diphtheriae. Under high-iron conditions, DtxR represses the synthesis of diphtheria toxin, corynebacterial siderophore, and other components of the high-affinity iron uptake system. Three DtxR-regulated promoter/operators designated tox, IRP1, and IRP2 were reported previously. In this study, we identified and characterized three additional DtxR-regulated promoter/operators from C. diphtheriae designated IRP3, IRP4, and IRP5. When beta-galactosidase was expressed from these three new promoter/ operators in Escherichia coli containing dtxR+ on pDSK29, enzyme levels were 5- to 30-fold lower during high-iron growth than during low-iron growth. In gel shift assays, the mobility of DNA fragments containing each promoter/operator decreased in the presence of purified DtxR and Co2+. In footprinting assays, DtxR protected 36-, 35-, and 30-bp regions of IRP3, IRP4, and IRP5, respectively, from cleavage by DNase I. In the 19-bp core of each promoter/operator, 12 or 13 bp matched the consensus for the DtxR-binding site. The putative polypeptides encoded by the open reading frames (ORFs) downstream from IRP3 and IRP4 were homologous, respectively, to several bacterial transcriptional regulators and to the deduced polypeptide encoded by an ORF located between the E. coli genes for primosomal replication protein N and adenine phosphoribosyltransferase. The putative polypeptide encoded by the ORF downstream from IRP5 was not homologous to any sequence in the protein database at the National Center for Biotechnology Information. When the ORFs downstream from IRP3 and IRP4 were expressed under the control of the phage T7 promoter in E. coli, polypeptide products of the predicted sizes were detected in small amounts by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
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PMID:Identification and characterization of three new promoter/operators from Corynebacterium diphtheriae that are regulated by the diphtheria toxin repressor (DtxR) and iron. 931 37

Regulation of gene expression in the mother cell compartment of sporulating Bacillus subtilis involves sequential activation and inactivation of several transcription factors. Among them are two sigma factors, sigmaE and sigmaK, and a DNA-binding protein, SpoIIID. A decrease in the level of SpoIIID is thought to relieve its repressive effect on transcription by sigmaK RNA polymerase of certain spore coat genes. Previous studies showed that sigmaK negatively regulates the level of spoIIID mRNA. Here, it is shown that sigmaK does not affect the stability of spoIIID mRNA. Rather, sigmaK appears to negatively regulate the synthesis of spoIIID mRNA by accelerating the disappearance of sigmaE RNA polymerase, which transcribes spoIIID. As sigmaK begins to accumulate by 4 h into sporulation, the sigmaE level drops rapidly in wild-type cells but remains twofold to fivefold higher in sigK mutant cells during the subsequent 4 h. In a strain engineered to produce sigmaK 1 h earlier than normal, twofold less sigmaE than that in wild-type cells accumulates. SigmaK did not detectably alter the stability of sigmaE in pulse-chase experiments. However, beta-galactosidase expression from a sigE-lacZ transcriptional fusion showed a pattern similar to the level of sigmaE protein in sigK mutant cells and cells prematurely expressing sigmaK. These results suggest that the appearance of sigmaK initiates a negative feedback loop controlling not only transcription of spoIIID, but the entire sigmaE regulon, by directly or indirectly inhibiting the transcription of sigE.
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PMID:A feedback loop regulates the switch from one sigma factor to the next in the cascade controlling Bacillus subtilis mother cell gene expression. 932 64

The oligodendrocyte-type-2 astrocyte lineage (O-2A) comprises a progenitor cell that is able to differentiate into an oligodendrocyte or astrocyte in vitro. The lineage was originally identified in the neonatal rat central nervous system but evidence suggests that the equivalent O-2A lineage also exists in humans. Apart from its putative and widely studied role in glial repair, this cell type could potentially be involved in malignant glioma formation. In this study we demonstrate that a rat O-2A progenitor cell line carrying the bacterial beta-galactosidase reporter gene and transformed with the c-myc and H-ras oncogenes which has lost its differentiation capacity in vitro generates glioma-like growth after stereotactic injection into the adult rat brain. Tumour pathology was similar to human glioblastoma, suggesting that one of the pathways in the generation of human glioblastomas may be the transformation of adult O-2A progenitor cells. Parallel studies demonstrated the presence of a DNA-binding protein complex, termed APprog, in a panel of human glioma cell lines. This protein was initially identified in O-2A progenitor cells and not their differentiated progeny. These data lead us to propose that APprog could be used as an indicator of the lineage origin of gliomas.
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PMID:Oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells transformed with c-myc and H-ras form high-grade glioma after stereotactic injection into the rat brain. 977 21

The Salmonella gene spvR is regulated by RpoS, and encodes an autoregulatory DNA-binding protein of the LysR family, which is required for transcriptional activation of the virulence operon spvABCD. We found that the 12-bp sequence between codons 3 and 8 of spvR (12bp-box) increased the expression of spvR'-lacZ translational fusions by at least two orders of magnitude. The 12bp-box did not affect the level of expression of a transcriptional spvR'-lacZ fusion, as determined by measurement of beta-galactosidase activity and mRNA levels. This suggests that the 12bp-box does not play a major role at the transcriptional level. However, the amounts of both SpvR-LacZ hybrid protein and lacZ mRNA produced from a translational spvR'-lacZ fusion were significantly lower if the 12bp-box was removed. Thus, the 12bp-box directly or indirectly affects the amount of spvR'-lacZ mRNA produced from a translational fusion but not from a transcriptional fusion. The 12bp-box still appeared to be functional when the spvR'-lacZ mRNA was elongated at its 5' end. In that case, however, while the 12bp-box greatly reduced the level of downstream mRNA produced, it did not affect the level of upstream mRNA. The effect of the 12bp-box was not restricted to lacZ fusions because expression of a translational spvR'-gfp fusion was also decreased by removal of the 12bp-box. The sequence of the 12bp-box is complementary to a sequence near the decoding region of 16S rRNA thought to be involved in translation initiation. This box may thus function as a translational enhancer, in which case the effect of the 12bp-box on lacZ mRNA levels might result indirectly from the tight coupling of translation and mRNA degradation. However, a direct role of the 12bp-box in increasing mRNA stability or in reducing the incidence of premature termination of transcription cannot be excluded.
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PMID:A coding segment of the virulence regulatory gene spvR enhances expression of spvR-lacZ and spvR-gfp translational fusions in Salmonella typhimurium. 1032 27

Open reading frame orf192, which is located immediately upstream of the aerobic repressor gene crtJ, was genetically and biochemically demonstrated to code for a second aerobic repressor (AerR) of photosynthesis gene expression in Rhodobacter capsulatus. Promoter-mapping studies indicate that crtJ has its own promoter but that a significant proportion of crtJ expression is promoted by read-through transcription of orf192 (aerR) transcripts through crtJ. Disruption of aerR resulted in increased photopigment biosynthesis during aerobic growth to a level similar to that of disruption of crtJ. Like that reported for CrtJ, beta-galactosidase assays of reporter gene expression indicated that disruption of aerR resulted in a two- to threefold increase in aerobic expression of the crtI and pucB operons. However, unlike CrtJ, AerR aerobically represses puf operon expression and does not aerobically repress bchC expression. Gel mobility shift analysis with purified AerR indicates that AerR does not bind to a bchC promoter probe but does bind to the crtI, puc, and puf promoter probes. These results indicate that AerR is a DNA-binding protein that targets genes partially overlapping a subset of genes that are also controlled by CrtJ. We also provide evidence for cooperative binding of AerR and CrtJ to the puc promoter region.
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PMID:AerR, a second aerobic repressor of photosynthesis gene expression in Rhodobacter capsulatus. 1197 10

The 14-kDa Vpr protein of human immunodeficiency virus type 1 (HIV-1) serves multiple functions in the retroviral life cycle, including the enhancement of viral replication in nondividing macrophages, the induction of G2 cell-cycle arrest in proliferating T lymphocytes, and the modulation of HIV-1-induced apoptosis. Extracellular Vpr has been detected in the sera and cerebral spinal fluid of HIV-infected patients. However, it is not known whether such forms of Vpr are biologically active. Vpr contains a carboxy-terminal basic amino acid rich segment stretch that is homologous to domains that mediate the energy- and receptor-independent cellular uptake of polypeptides by a process termed protein transduction. Similar functional protein-transducing domains are present in HIV-1 Tat, herpes simplex virus-1 DNA-binding protein VP22, and the Drosophila antennapedia homeotic transcription factor. We now demonstrate effective transduction of biologically active, synthetic Vpr (sVpr) as well as the Vpr-beta-galactosidase fusion protein. However, in contrast to other transducing proteins, Vpr transduction is not enhanced by protein denaturation, and Vpr's carboxy-terminal basic domain alone is not sufficient for its transduction across biological membranes. In contrast, the full-length Vpr protein effectively transduces a broad array of cells, leading to dose-dependent G2 cell-cycle arrest and apoptosis. Addition of Vpr into the extracellular medium also rescues the replication of Vpr-deficient strains of HIV-1 in human macrophage cultures. Native Vpr may thus be optimized for protein transduction, a feature that might enhance and extend the pathological effects of HIV infection.
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PMID:HIV-1 Vpr displays natural protein-transducing properties: implications for viral pathogenesis. 1242 19

Satb2 is a DNA-binding protein that regulates chromatin organization and gene expression. In the developing brain, Satb2 is expressed in cortical neurons that extend axons across the corpus callosum. To assess the role of Satb2 in neurons, we analyzed mice in which the Satb2 locus was disrupted by insertion of a LacZ gene. In mutant mice, beta-galactosidase-labeled axons are absent from the corpus callosum and instead descend along the corticospinal tract. Satb2 mutant neurons acquire expression of Ctip2, a transcription factor that is necessary and sufficient for the extension of subcortical projections by cortical neurons. Conversely, ectopic expression of Satb2 in neural stem cells markedly decreases Ctip2 expression. Finally, we find that Satb2 binds directly to regulatory regions of Ctip2 and induces changes in chromatin structure. These data suggest that Satb2 functions as a repressor of Ctip2 and regulatory determinant of corticocortical connections in the developing cerebral cortex.
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PMID:Satb2 regulates callosal projection neuron identity in the developing cerebral cortex. 1825 30

Plasmid pLALA was constructed for glycerol or glycerol-3-phosphate inducible plasmid-borne gene expression in Bacillus subtilis and closely related Gram-positive bacteria. Gene expression using pLALA is based on anti-termination of transcription and involves the B. subtilis GlpP protein that in the presence of glycerol-3-phosphate acts as an anti-terminator protein by binding to the 5'-untranslated region of glpD mRNA. Properties and the usefulness of the system, denoted LALA, were validated by inducible production in B. subtilis strains of two water-soluble proteins (beta-galactosidase and a protein phospho-tyrosine phosphatase), and one integral membrane protein (heme A synthase). Advantages with LALA is that it is based on positive control, does not involve a DNA-binding protein, and that glycerol, a cheap and stable compound, can be used as inducer of gene expression.
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PMID:Positively regulated glycerol/G3P-dependent Bacillus subtilis gene expression system based on anti-termination. 1894 4


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