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)

Infection with Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, may cause acute encephalitis in humans and induce severe cytopathic effects in various types of cultured cells. We observed that JEV replication rendered infected baby hamster kidney (BHK-21) cells sensitive to the translational inhibitor hygromycin B or alpha-sarcine, to which mock-infected cells were insensitive. However, little is known about whether any JEV nonstructural (NS) proteins contribute to virus-induced changes in membrane permeability. Using an inducible Escherichia coli system, we investigated which parts of JEV NS1 to NS4 are capable of modifying membrane penetrability. We found that overexpression of NS2B-NS3, the JEV protease, permeabilized bacterial cells to hygromycin B whereas NS1 expression failed to do so. When expressed separately, NS2B alone, but not NS3, was sufficient to alter bacterial membrane permeability. Similarly, expression of NS4A or NS4B also rendered bacteria susceptible to hygromycin B inhibition. Examination of the effect of NS1 to NS4 expression on bacterial growth rate showed that NS2B exhibited the greatest inhibitory capability, followed by a modest repression from NS2A and NS4A, whereas NS1, NS3, and NS4B had only trivial influence with respect to the vector control. Furthermore, when cotransfected with a reporter gene luciferase or beta-galactosidase, transient expression of NS2A, NS2B, and NS4B markedly reduced the reporter activity in BHK-21 cells. Together, our results suggest that upon JEV infection, these four small hydrophobic NS proteins have various modification effects on host cell membrane permeability, thereby contributing in part to virus-induced cytopathic effects in infected cells.
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PMID:Membrane permeabilization by small hydrophobic nonstructural proteins of Japanese encephalitis virus. 1040 Jul 16

Aedes aegypti densonucleosis virus (AeDNV) has two promoters that have been shown to be active by reporter gene expression analysis (B. N. Afanasiev, Y. V. Koslov, J. O. Carlson, and B. J. Beaty, Exp. Parasitol. 79:322-339, 1994). Northern blot analysis of cells infected with AeDNV revealed two transcripts 1,200 and 3,500 nucleotides in length that are assumed to express the structural protein (VP) gene and nonstructural protein genes, respectively. Primer extension was used to map the transcriptional start site of the structural protein gene. Surprisingly, the structural protein gene transcript began at an initiator consensus sequence, CAGT, 60 nucleotides upstream from the map unit 61 TATAA sequence previously thought to define the promoter. Constructs with the beta-galactosidase gene fused to the structural protein gene were used to determine elements necessary for promoter function. Deletion or mutation of the initiator sequence, CAGT, reduced protein expression by 93%, whereas mutation of the TATAA sequence at map unit 61 had little effect. An additional open reading frame was observed upstream of the structural protein gene that can express beta-galactosidase at a low level (20% of that of VP fusions). Expression of the AeDNV structural protein gene was shown to be stimulated by the major nonstructural protein NS1 (Afanasiev et al., Exp. parasitol., 1994). To determine the sequences required for transactivation, expression of structural protein gene-beta-galactosidase gene fusion constructs differing in AeDNV genome content was measured with and without NS1. The presence of NS1 led to an 8- to 10-fold increase in expression when either genomic end was present, compared to a 2-fold increase with a construct lacking the genomic ends. An even higher (37-fold) increase in expression occurred with both genomic ends present; however, this was in part due to template replication as shown by Southern blot analysis. These data indicate the location and importance of various elements necessary for efficient protein expression and transactivation from the structural protein gene promoter of AeDNV.
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PMID:Characterization of the structural gene promoter of Aedes aegypti densovirus. 1115 5

We have previously reported successful trans-complementation of defective Kunjin virus genomic RNAs with a range of large lethal deletions in the nonstructural genes NS1, NS3, and NS5 (A. A. Khromykh et al., J. Virol. 74:3253-3263, 2000). In this study we have mapped further the minimal region in the NS5 gene essential for efficient trans-complementation of genome-length RNAs in repBHK cells to the first 316 of the 905 codons. To allow amplification and easy detection of complemented defective RNAs with deletions apparently affecting virus assembly, we have developed a dual replicon complementation system. In this system defective replicon RNAs with a deletion(s) in the nonstructural genes also encoded the puromycin resistance gene (PAC gene) and the reporter gene for beta-galactosidase (beta-Gal). Complementation of these defective replicon RNAs in repBHK cells resulted in expression of PAC and beta-Gal which allowed establishment of cell lines stably producing replicating defective RNAs by selection with puromycin and comparison of replication efficiencies of complemented defective RNAs by beta-Gal assay. Using this system we demonstrated that deletions in the C-terminal 434 codons of NS3 (codons 178 to 611) were complemented for RNA replication, while any deletions in the first 178 codons were not. None of the genome-length RNAs containing deletions in NS3 shown to be complementable for RNA replication produced secreted defective viruses during complementation in repBHK cells. In contrast, structural proteins produced from these complemented defective RNAs were able to package helper replicon RNA. The results define minimal regions in the NS3 and NS5 genes essential for the formation of complementable replication complex and show a requirement of NS3 in cis for virus assembly.
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PMID:Complementation analysis of the flavivirus Kunjin NS3 and NS5 proteins defines the minimal regions essential for formation of a replication complex and shows a requirement of NS3 in cis for virus assembly. 1236 19

Influenza A virus NS1 protein is an important regulatory factor with multiple functions and contributes greatly to viral pathogenesis. In the present study, transcription-activating potential of NS1 from different influenza A virus subtypes was examined in yeast two-hybrid system. The bait vectors containing different NS1 genes, along with an empty prey vector, were transformed into yeast AH109(for growth assay on QDO plate and alpha-galactosidase assay), and Y187(for beta-galactosidase assay). AH109 transformants with NS1 gene from H1N1, H5N1, and H9N2 viruses grew vigorously on the QDO plate and secreted high level of alpha-galactosidase. Also, Y187 bearing the above NS1 genes exhibited enhanced beta-galactosidase activity. Nevertheless, H3N2-NS1-transformed AH109 and Y187 yeasts did not grow on QDO plate and secrete beta-galactosidase, respectively. These findings denote the remarkable variation in NS1 proteins from different influenza A virus subtypes on the transcription-stimulating capability in yeast.
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PMID:Differential transcription-activating capability of NS1 proteins from different influenza virus subtypes expressed in yeast. 1955 32


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