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)

To learn if an mRNA.18S rRNA interaction or a special secondary structure in the mRNA start region is essential for translation in eukaryotic cells, we constructed recombinant plasmids with the SV40 early promoter 5' to part of the Escherichia coli tufB-lacZ gene. Deletion of bases potentially complementary to the 18S rRNA highly increased the transient beta-galactosidase expressed in transfected CHO cells. Deletion of bases that fostered formation of potential hairpins with the mRNA 5'-terminus or altered the structure of the coding region reduced beta-galactosidase activity suggesting that these features of the mRNA secondary structure may be essential for initiation of translation. Computer aided analysis of the potential structure of 290 mRNAs suggests these are conserved features of the initiation region.
Mol Biol Rep 1992 Sep
PMID:Effect of deletions 5' to the translation initiation sequence on the expression of an mRNA in animal cells. 145 61

Grafts of various types of cells have been performed using bioresorbable polymer matrices. These synthetic fibers are degraded by hydrolysis into normal metabolic intermediates and induce a number of events that are conductive to healing and/or repair, the most important of which may be angiogenesis. The use of biodegradable meshes to deliver genetically altered cells was studied. A beta-galactosidase gene was inserted into Long-Evans rat bone marrow stromal (BMS) cells or fibroblasts derived from C57BL/6J mouse embryos using the retroviral vector LNL-SLX beta gal. Expression was monitored using X-gal staining. X-gal+ cells from monolayer cultures were seeded onto either polyglycolic acid (PGA) or polyglactin (PGL) biodegradable meshes and grown to confluence. Two types of grafts were performed: (1) embryonic C57BL/6J mouse fibroblasts (EMF) into either nude mice or adult C57BL/6J mice, and (2) Long-Evans rat BMS into Long-Evans rats. Beta-Galactosidase activity was found for up to 152 days for EMF in nude mice, 123 days for EMF in adult C57BL/6J mice, and 90 days for grafts of syngeneic BMS cells into Long-Evans rats. Noninfected cells grafted using the same methods did not stain with X-gal.
Somat Cell Mol Genet 1992 Sep
PMID:Long-term expression of a retrovirally introduced beta-galactosidase gene in rodent cells implanted in vivo using biodegradable polymer meshes. 147 11

The dopamine beta-hydroxylase promoter has been shown to direct expression of the reporter gene product, beta-galactosidase, to enteric neurons and putative embryonic neuroblasts in transgenic mice (Mercer et al., 1991; Kapur et al., 1991). In this paper, expression of the transgene, D beta H-nlacZ, in the gastrointestinal tract is characterized in more detail in wild-type mice and mice which are also homozygous for the lethal spotted allele (ls). Expression of the transgene in wild-type embryos was first detected in scattered mesenchymal cells in the proximal foregut on embryonic day 9.5, and progressed distally until embryonic day 13.5 when the entire length of the gut was colonized by such cells. Several observations suggest that the mesenchymal cells which express the transgene (MCET) are, in fact, enteric neuroblasts, probably derived from the vagal neural crest. (1) The presence of MCET in progressively more caudal portions of the embryonic gut correlated with the neurogenic potential of isolated gastrointestinal segments grafted under the renal capsule. (2) Mitotic activity of MCET was demonstrated by incorporation of [3H]thymidine in utero. (3) The migratory behavior of MCET and/or their precursors was revealed in anastomotic subcapsular grafts of gut from transgenic and non-transgenic embryos; enteric ganglia of the latter were populated by MCET from the former. (4) Enteric expression of the transgene postnatally was restricted to intrinsic neurons that coexpressed other phenotypic markers of neuronal differentiation. The pattern of transgene expression in ls/ls mice was identical to that seen in ls/+ and +/+ mice until embryonic day 12.5.(ABSTRACT TRUNCATED AT 250 WORDS)
Development 1992 Sep
PMID:A transgenic model for studying development of the enteric nervous system in normal and aganglionic mice. 148 85

A Plasmodium falciparum genomic DNA library was established in the expression vector lambda gt11, cloned in Escherichia coli. The library was screened with human hyperimmune sera by in situ hybridization. Twenty clones expressing P. falciparum sequences as polypeptides fused to beta-galactosidase were identified. One, CD3A/9025/60, reacted with all immune sera and expressed polypeptides that were larger than beta-galactosidase as well as reacting with antibodies to beta-galactosidase and to P. falciparum. When the fusion proteins were used as target antigens to diagnose malaria antibodies, a result was obtained which correlated well with indirect fluorescence assay.
Southeast Asian J Trop Med Public Health 1992 Sep
PMID:Molecular cloning of Plasmodium falciparum blood stage antigens and application of the recombinant proteins in serodiagnosis. 148 92

Poly(ADP-ribose) polymerase (PARP, EC 2.4.2.30) is a zinc finger DNA-binding protein involved in DNA repair processes in eukaryotes. By deletion and extensive site-directed mutagenesis, its DNA-binding domain fused to the N-terminus of beta-galactosidase was shown to contain a nuclear localization signal (NLS) of the form KRK-X(11)-KKKSKK (residues 207-226). In vitro, both the DNA-binding capacity and the polymerizing activity of PARP are independent of the nuclear location function. Each basic cluster is essential but not sufficient on its own for this function, while both motifs together are. Crucial basic amino acids (K207, R208 and K222) in each of these two motifs are required for nuclear homing. The results presented here support the concept that the human PARP NLS is an autonomous functional element and belongs to the class of bipartite NLSs. We show that the linear distance between the two basic clusters is not crucial. Insertional mutation analysis leading to a partial reversion of the cytoplasmic phenotype displayed by the mutant K222I highlights the crucial positioning of this lysine. The structure-function relationship of the second cluster of basic residues is discussed.
EMBO J 1992 Sep
PMID:The human poly(ADP-ribose) polymerase nuclear localization signal is a bipartite element functionally separate from DNA binding and catalytic activity. 150 17

We investigated the use of the prokaryotic tetracycline operator-repressor system as a regulatory device to control the expression of Dictyostelium discoideum tRNA genes. The tetO1 operator fragment was inserted at three different positions in front of a tRNA(Glu) (Am) suppressor gene from D. discoideum, and the tetracycline repressor gene was expressed under the control of a constitutive actin 6 promoter. The effectiveness of this approach was determined by monitoring the expression of a beta-galactosidase gene engineered to contain a stop codon that could be suppressed by the tRNA. When these constructs were introduced into Dictyostelium cells, the repressor bound to the operator in front of the tRNA gene and prevented expression of the suppressor tRNA. Addition of tetracycline (30 micrograms/ml) to the growth medium prevented repressor binding, allowed expression of the suppressor tRNA, and resulted in beta-galactosidase synthesis. The operator-repressor complex interfered with tRNA gene transcription when the operator was inserted immediately upstream (position +1 or -7) of the mature tRNA coding region. Expression of a tRNA gene carrying the operator at position -46 did not respond to repressor binding. This system could be used to control the synthesis of any protein, provided the gene contained a translational stop signal.
Mol Cell Biol 1992 Sep
PMID:Establishment of a system for conditional gene expression using an inducible tRNA suppressor gene. 150 1

The LAC4 gene encoding the beta-galactosidase (beta Gal) of the yeast, Kluyveromyces lactis, was cloned on a 7.2-kb fragment by complementation of a lacZ-deficient Escherichia coli strain. The nucleotide sequence of the structural gene, with 42 bp and 583 bp of the 5'- and 3'-flanking sequences, respectively, was determined. The deduced amino acid (aa) sequence of the K. lactis beta Gal predicts a 1025-aa polypeptide with a calculated M(r) of 117618 and reveals extended sequence homologies with all the published prokaryotic beta Gal sequences. This suggests that the eukaryotic beta Gal is closely related, evolutionarily and structurally, to the prokaryotic beta Gal's. In addition, sequence similarities were observed between the highly conserved N-terminal two-thirds of the beta Gal and the entire length of the beta-glucuronidase (beta Glu) polypeptides, which suggests that beta Glu is clearly related, structurally and evolutionarily, to the N-terminal two-thirds of the beta Gal. The structural analysis of the beta Gal alignment, performed by mean secondary structure prediction, revealed that most of the invariant residues are located in turn or loop structures. The location of the invariant residues is discussed with respect to their accessibility and their possible involvement in the catalytic process.
Gene 1992 Sep 01
PMID:Sequence of the Kluyveromyces lactis beta-galactosidase: comparison with prokaryotic enzymes and secondary structure analysis. 151 85

We have used fusions of the outer membrane protein LamB to beta-galactosidase (encoded by lacZ) to study the protein export process. This LamB-LacZ hybrid protein blocks export when synthesized at high levels, as evidenced by inducer (maltose) sensitivity, a phenomenon termed LacZ hybrid jamming. The prlF1 mutation relieves LacZ hybrid jamming and allows localization of the fusion protein to a noncytoplasmic compartment. prlF1 and similar alleles are gain-of-function mutations. Null mutations in this gene confer no obvious phenotypes. Extragenic suppressors of a gain-of-function prlF allele have been isolated in order to understand how this gene product affects the export process. The suppressors are all lon null mutations, and they are epistatic to all prlF phenotypes tested. Lon protease activity has been measured in prlF1 cells and shown to be increased. However, the synthesis of Lon is not increased in a prlF1 background, suggesting a previously unidentified mechanism of Lon activation. Further analysis reveals that prlF1 activates degradation of cytoplasmically localized precursors in a Lon protease-dependent manner. It is proposed that accumulation of precursors during conditions of hybrid protein jamming titrates an essential export component(s), possibly a chaperone. Increased Lon-dependent precursor degradation would free this component, thus allowing increased protein export under jamming conditions.
J Bacteriol 1992 Sep
PMID:Enhanced export of beta-galactosidase fusion proteins in prlF mutants is Lon dependent. 151 98

Stable transformants of mammalian cells from gene transfer often show extreme variability in expression of the introduced transgene. This occurs from the highly variable number of copies integrated into the genome and from position effects on gene expression due to random integration. We have eliminated both of these constraints on predictable gene expression by use of a lox recombination vector. The positive selection vector system is designed to directly select Cre-mediated DNA integration at a lox target previously placed into the genome of cultured mammalian cells. Proper targeting activates expression of a defective lox-neomycin phosphotransferase (neo) fusion gene target. With CHO cell lines containing this target, almost all of the selected transformants (54 of 56 independent G418-resistant colonies) were simple single-copy integrants of the targeting DNA. To monitor gene expression at a single chromosomal site, we used a beta-actin promoter-lacZ reporter construct. Independent G418-resistant colonies from site-specific integration of the reporter gene all showed nearly identical levels of beta-galactosidase activity when the reporter construct integrated at a particular chromosomal position. The same construct integrated at a second chromosomal position exhibited a slightly different level of activity, characteristic of that second position. These results show that Cre-mediated site-specific integration can facilitate the construction of isogenic cell lines and thereby permit reproducible gene expression in stably transformed cell lines.
Proc Natl Acad Sci U S A 1992 Sep 01
PMID:Genomic targeting with a positive-selection lox integration vector allows highly reproducible gene expression in mammalian cells. 151 11

Complexes containing plasmid DNA, transferrin-polylysine conjugates, and polylysine-conjugated peptides derived from the N-terminal sequence of the influenza virus hemagglutinin subunit HA-2 have been used for the transfer of luciferase or beta-galactosidase marker genes to K562 cells, HeLa cells, and BNL CL.2 hepatocytes. These DNA complexes mimic the entry of viruses into cells, as they contain functions for (i) the packaging of the nucleic acid with polylysine, (ii) the attachment to the cell and receptor-mediated endocytosis with transferrin as a ligand, and (iii) the release from endosomes by using membrane-disrupting influenza peptides. The presence of these influenza peptide conjugates in the DNA complexes renders the complexes active in membrane disruption in a liposome leakage assay and results in a substantial augmentation of the transferrin-polylysine-mediated gene transfer.
Proc Natl Acad Sci U S A 1992 Sep 01
PMID:Influenza virus hemagglutinin HA-2 N-terminal fusogenic peptides augment gene transfer by transferrin-polylysine-DNA complexes: toward a synthetic virus-like gene-transfer vehicle. 151 16


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