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)

The SKI2 gene is part of a host system that represses the copy number of the L-A double-stranded RNA (dsRNA) virus and its satellites M and X dsRNA, of the L-BC dsRNA virus, and of the single-stranded replicon 20S RNA. We show that SKI2 encodes a 145-kDa protein with motifs characteristic of helicases and nucleolar proteins and is essential only in cells carrying M dsRNA. Unexpectedly, Ski2p does not repress M1 dsRNA copy number when M1 is supported by aN L-A cDNA clone; nonetheless, it did lower the levels of M1 dsRNA-encoded toxin produced. Since toxin secretion from cDNA clones of M1 is unaffected by Ski2p, these data suggest that Ski2p acts by specifically blocking translation of viral mRNAs, perhaps recognizing the absence of cap or poly(A). In support of this idea, we find that Ski2p represses production of beta-galactosidase from RNA polymerase I [no cap and no poly(A)] transcripts but not from RNA polymerase II (capped) transcripts.
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PMID:Evidence that the SKI antiviral system of Saccharomyces cerevisiae acts by blocking expression of viral mRNA. 832 Dec 35

PpLSU3, a mobile group I intron found in the ribo-somal RNA genes of Physarum polycephalum, encodes the I-PpoI homing endonuclease. This enzyme represents one of the rare cases in nature where a protein is expressed from an RNA polymerase I transcript. Our previous results showed that the full length intron, but not a further processed species, is the messenger for I-PpoI, implying a role of the untranslated region (UTR) in gene expression. To study the function of the 3'-UTR in expression of the endonuclease and in splicing of the intron, we replaced the I-PpoI gene in PpLSU3 with the gene for the alpha-fragment of Escherichia coli beta-galactosidase, and then integrated this chimeric intron into all the chromosomal rDNA repeats of yeast. The resulting cells synthesized functional alpha-fragment, as evidenced by a complementation assay analogous to that used in E.coli. The beta-galactosidase activity thus provides an unusual and potentially valuable readout for Pol I transcription from chromosomal rDNA. This is the first example in which a eucaryotic homing endonuclease gene has been successfully replaced by a heterologous gene. Using deletion mutagenesis and a novel randomization approach with the alpha-fragment as a reporter, we found that a small segment of the 3'-UTR dramatically influences both splicing and protein expression.
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PMID:Functional alpha-fragment of beta-galactosidase can be expressed from the mobile group I intron PpLSU3 embedded in yeast pre-ribosomal RNA derived from the chromosomal rDNA locus. 1068 39

This report describes the construction of a DNA cassette for integration into a genomic small sub-unit rRNA locus of Leishmania mexicana by homologous recombination. Reporter genes encoding beta-galactosidase or green fluorescent protein and the gene conferring hygromycin resistance were integrated downstream of a RNA polymerase I-driven rRNA promoter. To ensure high expression of the marker proteins in the intracellular, amastigote stage, transgene coding sequences were followed by the intergenic region of the L. mexicana cysteine proteinase B 2.8 gene which provides processing signals required for high level expression in this life-cycle stage. Integration of the DNA cassette was also efficiently obtained in L. major. We show that either beta-galactosidase or the green fluorescent protein were abundantly, stably and uniformly expressed in promastigotes and amastigotes of both Leishmania sp. The transgenic lines allow parasite detection at high sensitivity in the tissues of infected mice and will be useful to follow infections in macrophages in culture and in animal hosts.
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PMID:Targeted integration into a rRNA locus results in uniform and high level expression of transgenes in Leishmania amastigotes. 1077 1

An enhancer-like element VV16 from Vaccinia virus genome DNA was obtained by using the plasmid with CAT reporter gene. Sequence analysis showed the element of 112 bp is a part of the DNA-dependent RNA polymerase, polyA polymerase and DNA polymerase (RPO30 gene). It contains 4 AT-rich regions. Detection of beta-galactosidase activity showed that VV16 in the positive direction can increase the activity 9.0 times and VV16 in the negative direction can increase 4.1 times. The RNA dot blotting confirmed the enhancing activity of the element are on the transcription level. DNA deletion experiment indicated the sequences of 10 bp at the 5' end and 12 bp at the 3' end in the element are important to its function and the sequence from nt76 to nt82 is essential to its activity.
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PMID:[Functional and structural study of the prokaryotic enhancer-like element VV16 from vaccinia virus genome]. 1105 76

Holomycin, a member of the pyrrothine class of antibiotics, displayed broad-spectrum antibacterial activity, inhibiting a variety of gram-positive and gram-negative bacteria, with the exception of Enterobacter cloacae, Morganella morganii, and Pseudomonas aeruginosa. The antibiotic lacked activity against the eukaryotic microorganisms Saccharomyces cerevisiae and Candida kefyr. Holomycin exhibited a bacteriostatic response against Escherichia coli that was associated with rapid inhibition of RNA synthesis in whole cells. Inhibition of RNA synthesis could have been a secondary consequence of inhibiting tRNA aminoacylation, thereby inducing the stringent response. However, the levels of inhibition of RNA synthesis by holomycin were similar in a stringent and relaxed pair of E. coli strains that were isogenic except for the deletion of the relA gene. This suggests that inhibition of RNA synthesis by holomycin could reflect direct inhibition of DNA-dependent RNA polymerase. Examination of the effects of holomycin on the kinetics of the appearance of beta-galactosidase in induced E. coli cells was also consistent with inhibition of RNA polymerase at the level of RNA chain elongation. However, holomycin only weakly inhibited E. coli RNA polymerase in assays using synthetic poly(dA-dT) and plasmid templates. Furthermore, inhibition of RNA polymerase was observed only at holomycin concentrations in excess of those required to inhibit the growth of E. coli. It is possible that holomycin is a prodrug, requiring conversion in the cell to an active species that inhibits RNA polymerase.
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PMID:Antimicrobial properties and mode of action of the pyrrothine holomycin. 1115 51