The long terminl repeat(LTR) of the bovine foamy virus(BFV) contains the viral promoter,which is responsible for viral gene expression in eukaryotic cells We have demonstrated that BFV LTR linked to the luciferase gen...The long terminl repeat(LTR) of the bovine foamy virus(BFV) contains the viral promoter,which is responsible for viral gene expression in eukaryotic cells We have demonstrated that BFV LTR linked to the luciferase gene can express the enzyme efficiently upon transformation into bacteria Deletion analysis and sequence comparison showed that the BFV LTR has a sequence(from-125 to-90)which is greatly homologous to the model bacteria promoter And the proposed transcriptional starting site is at the thymine of-91 or the cytosine of -92 Besides,being fully functional in E coli,the BFV LTR can also be specifically trans activated by BFV tas gene product,Borf-1 protein The responsive element lies between base -310 and -140,which is in accordance with the responsive region in eukaryotic cells The trans-activation of BFV LTR by Borf 1 protein in bacteria offers a useful system to investigate further the specific interaction between Borf-1 protein with BFV LTR and the mechanism of the trans展开更多
Bovine foamy virus (BFV), a member of the spumavirus subfamily of retroviruses,contains two open reading frames (ORF-1 and ORF-2) in addition to the genes coding for gag,po/and env. Borf-1 protein, encoded by BFV ORF-...Bovine foamy virus (BFV), a member of the spumavirus subfamily of retroviruses,contains two open reading frames (ORF-1 and ORF-2) in addition to the genes coding for gag,po/and env. Borf-1 protein, encoded by BFV ORF-1, is identified as a transcriptional transactivator, which augments gene expression directed by the viral long terminal repeat (LTR).Further investigations in transient expression assays reveal that the Borf-1 responsive elements are located in the U3 domain of the LTR, upstream from position -140 ( + 1 represents the transcription initiation site), and the BFV RU5 region has an inhibitory effect in LTR-directed gene expression.展开更多
Bovine foamy virus encodes a transcriptional transactivitor, Tas or Borf-1, which governs the level of viral transcripts initiated by both the promoter in the long terminal repeat (LTR) and the internal promoter (IP) ...Bovine foamy virus encodes a transcriptional transactivitor, Tas or Borf-1, which governs the level of viral transcripts initiated by both the promoter in the long terminal repeat (LTR) and the internal promoter (IP) located in the env gene through their cis-acting targets. We have identified and characterized a 72 bp TBS (Borf-1) responsive element located in BFV3026, internal promoter (TREIP) by deletion mutant and transient expression assay. This cis-acting target element in the internal promoter has the properties of a transcriptional enhancer which functions independently of its orientation, position and also in heterologous promoters (BFV LTR and bovine immunodeficiency virus, BIV LTR). Alignments reveal that there are positional similarity and sequence homology among BFV TREIP, SFV-1 TREIP proximal element and SFV-3 TREIPH, which suggests that this kind of cis-acting elements possesses some common functional character.展开更多
Foamy viruses(FVs)have broad cellular tropism infecting vertebrates from fish to human being,which indicates that Env protein has a high capability for membrane fusion.Conservative features in all FV transmembrane(TM)...Foamy viruses(FVs)have broad cellular tropism infecting vertebrates from fish to human being,which indicates that Env protein has a high capability for membrane fusion.Conservative features in all FV transmembrane(TM)proteins include a region of hydrophobic domain called membrane-spanning domain(MSD),which contains several stretches of hydrophobic amino acids.To investigate whether these features were associated with the cytotoxicity effect of TM on Escherichia coli,a series of mutants were constructed and expressed in the E.coli BL21(DE3)using pET-32a(+)as expressing vector.The results showed that only TM3 without MSD was expressed in E.coli,whereas the other two containing full or part of the MSD(TM1 and TM2)could not be expressed.Furthermore,the bacterial amount and living bacteria analysis revealed that the cytotoxicity of TM was dependent on its MSD,especially on the stretches of hydrophobic amino acids.Western blotting analysis showed that TM3 protein was purified with affinity purification.展开更多
文摘The long terminl repeat(LTR) of the bovine foamy virus(BFV) contains the viral promoter,which is responsible for viral gene expression in eukaryotic cells We have demonstrated that BFV LTR linked to the luciferase gene can express the enzyme efficiently upon transformation into bacteria Deletion analysis and sequence comparison showed that the BFV LTR has a sequence(from-125 to-90)which is greatly homologous to the model bacteria promoter And the proposed transcriptional starting site is at the thymine of-91 or the cytosine of -92 Besides,being fully functional in E coli,the BFV LTR can also be specifically trans activated by BFV tas gene product,Borf-1 protein The responsive element lies between base -310 and -140,which is in accordance with the responsive region in eukaryotic cells The trans-activation of BFV LTR by Borf 1 protein in bacteria offers a useful system to investigate further the specific interaction between Borf-1 protein with BFV LTR and the mechanism of the trans
文摘Bovine foamy virus (BFV), a member of the spumavirus subfamily of retroviruses,contains two open reading frames (ORF-1 and ORF-2) in addition to the genes coding for gag,po/and env. Borf-1 protein, encoded by BFV ORF-1, is identified as a transcriptional transactivator, which augments gene expression directed by the viral long terminal repeat (LTR).Further investigations in transient expression assays reveal that the Borf-1 responsive elements are located in the U3 domain of the LTR, upstream from position -140 ( + 1 represents the transcription initiation site), and the BFV RU5 region has an inhibitory effect in LTR-directed gene expression.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 39970033 ) Doctoral Fund in High School (Grant No. 98005516).
文摘Bovine foamy virus encodes a transcriptional transactivitor, Tas or Borf-1, which governs the level of viral transcripts initiated by both the promoter in the long terminal repeat (LTR) and the internal promoter (IP) located in the env gene through their cis-acting targets. We have identified and characterized a 72 bp TBS (Borf-1) responsive element located in BFV3026, internal promoter (TREIP) by deletion mutant and transient expression assay. This cis-acting target element in the internal promoter has the properties of a transcriptional enhancer which functions independently of its orientation, position and also in heterologous promoters (BFV LTR and bovine immunodeficiency virus, BIV LTR). Alignments reveal that there are positional similarity and sequence homology among BFV TREIP, SFV-1 TREIP proximal element and SFV-3 TREIPH, which suggests that this kind of cis-acting elements possesses some common functional character.
基金This work was supported by National Natural Science Foundation for Youth(No.30100003).
文摘Foamy viruses(FVs)have broad cellular tropism infecting vertebrates from fish to human being,which indicates that Env protein has a high capability for membrane fusion.Conservative features in all FV transmembrane(TM)proteins include a region of hydrophobic domain called membrane-spanning domain(MSD),which contains several stretches of hydrophobic amino acids.To investigate whether these features were associated with the cytotoxicity effect of TM on Escherichia coli,a series of mutants were constructed and expressed in the E.coli BL21(DE3)using pET-32a(+)as expressing vector.The results showed that only TM3 without MSD was expressed in E.coli,whereas the other two containing full or part of the MSD(TM1 and TM2)could not be expressed.Furthermore,the bacterial amount and living bacteria analysis revealed that the cytotoxicity of TM was dependent on its MSD,especially on the stretches of hydrophobic amino acids.Western blotting analysis showed that TM3 protein was purified with affinity purification.
