Development of a novel vector for cloning and expressing extremely toxic genes in Escherichia coli

Background: Escherichia coli has been widely used as a host to clone and express heterologous genes. However, there are few vectors available for cloning and expressing extremely toxic genes, which limits further basic and applied research on extremely toxic proteins. Results: In this study, a novel vector pAU10 was constructed in E. coli. pAU10 utilizes the combination of the efficient but highly repressible T7-lacO promoter/operator and the strong rrnBT2 transcriptional terminator upstream of the T7 promoter to strictly control unwanted transcription of the extremely toxic gene; in addition, the trp promoter/operator is oriented opposite to the T7 promoter to control the production of the antisense RNA that may block the translation of leaky mRNA. Without the supplementation of IPTG and L-tryptophan in the culture medium, transcription of the extremely toxic gene by the T7 promoter is highly repressed, and the trp promoter produces the antisense RNA, which strictly prevents unwanted expression of the extremely toxic protein in E. coli. With the supplementation of IPTG and L-tryptophan, the T7 promoter efficiently transcribes the extremely toxic gene, and the trp promoter does not produce the antisense RNA, ensuring efficient expression of the extremely toxic protein in E. coli. Tight regulation and efficiency of expression of an extremely toxic gene cloned in the vector pAU10 were confirmed by cloning and expressing the restriction endonuclease-encoding gene bamHI without its corresponding methylase gene in E. coli JM109(DE3). Conclusion: pAU10 is a good vector used for cloning and expressing extremely toxic genes in E. coli.

Diagnostic value of serum levels of BamHI-W, LMP-1 and BZLF1 in NK/T-cell lymphoma / 中华血液学杂志

<p><b>OBJECTIVE</b>To explore the diagnostic value of serum levels of BamHI-W fragment, latent membrane protein-1 (LMP-1), BZLF1 and ZEBRA protein in patients with natural killer (NK)/T-cell lymphomas (NKTCLs), and to evaluate their relationship with clinical features.</p><p><b>METHODS</b>A total of 144 cases were analyzed in this study, including 48 NKTCLs patients, 48 other types of non-Hodgkin's lymphomas (NHL) patients and 48 healthy individuals as controls. Fluorescent quantitative real-time polymerase chain reaction (RQ-PCR) was used to measure the copy number of BamHI-W, LMP-1 and BZLF1 in serum. Enzyme linked immunosorbent assay (ELISA) was applied to measure the serum levels of ZEBRA protein. The relative operating characteristic (ROC) curve was applied in the evaluation of the tested markers in diagnosis of NKTCL patients, and the correlations among the tested markers and clinical feature were analyzed.</p><p><b>RESULTS</b>Compared with the controls, NKTCL group showed significantly higher levels of all the tested markers (P < 0.01). The median values of serum BamHI-W, LMP-1 and BZLF1 DNAs level were 1870, 394 and 499 copies/ml, respectively. And the median value of ZEBRA protein level was 73.3 µg/L. Furthermore, the ROC curves analysis revealed that all the area under curve (AUC) of LMP-1, BZLF1 and ZEBRA were more than 0.70, which were probably helpful in the diagnosis of NKTCL. To predict the presence of NKTCL, BamHI-W showed a high sensitivity of 81.3%, while BZLF1 showed a high specificity of 81.2%. Untreated patients seemed to have a significantly higher level of serum LMP1 DNA than that of treated patients (median value 898 copies/ml vs 0 copies/ml, P = 0.050). Correlation analysis showed that serum BamHI-W DNA level was correlated with the presence of B symptoms. All the three genes expressed in 94.4% of the untreated cases. On the other hand, none of them expressed in treated cases.</p><p><b>CONCLUSIONS</b>It suggested that combined measurements of BamHI W, LMP1 and BZLF1 DNA levels might be helpful to the diagnosis and therapeutic monitor of NKTCL.</p>

Analysis of Epstein-Barr virus with BamHI "f" variant and XhoI-loss of LMP1 gene in nasopharyngeal carcinoma / 中华病理学杂志

<p><b>OBJECTIVE</b>To investigate the genomic variation of Epstein-Barr virus (EBV) and its significance in nasopharyngeal carcinogenesis.</p><p><b>METHODS</b>Forty nasopharyngeal carcinoma (NPC) biopsy tissues were used for detection of EBV BamHI f variant and LMP1 XhoI-loss by polymerase chain reaction (PCR), nested PCR, and RFLP (restriction fragment length polymorphism). Forty-eight samples of peripheral blood mononuclear cells (PBMC) taken from apparently healthy adult individuals were used for detection of LMP1 XhoI-loss. Three samples of amplified LMP1 exon 1 DNA from B95-8 cell line and 2 NPC tissues (one having XhoI-loss and the other having Wt-XhoI/XhoI-loss) were sequenced.</p><p><b>RESULTS</b>Thirty out of the 40 NPC cases (30/40, 75%) harbored EBV BamHI f variant and the remaining 10 (10/40, 25%) harbored BamHI F prototype. Thirty out of the 39 NPCs (30/39, 76.9%) showed single EBV LMP1 XhoI-loss, 7 (7/39, 18.0%) showed single LMP1 Wt-XhoI (presence of a XhoI site in exon 1 of LMP1 gene, as in B95-8 cell line), and 2 (2/39, 5.1%) showed both LMP1 Wt-XhoI and XhoI-loss. Thirty-eight of the 39 NPCs (97.4%) showed EBV LMP1 XhoI-loss or/and BamHI F variant. In the NPC tissue (1 case only) showing the prototype of Wt-XhoI/BamHI "f", there were several base substitutions, including 5 missense mutations and 2 silent mutations present in LMP1 exon 3, on DNA sequencing. On the other hand, 10 out of the 48 samples of PBMC taken from apparently healthy individuals could be amplified successfully by nested PCR for detection of LMP1 XhoI site. All of these 10 samples carried the prototype of EBV LMP1 Wt-XhoI.</p><p><b>CONCLUSIONS</b>The majority of EBV present in neoplastic cells of NPC is of BamHI "f" variant and/or possesses LMP1 XhoI-loss, as compared with that in healthy individuals. This genomic variation of EBV may bear some roles in the development and progression of NPC.</p>

Cloning and polymorphism analysis of prtH gene from Porphyromonas gingivalis / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To clone the prtH gene from Porphyromonas gingivalis (P.g) ATCC 33277 and analyze the polymorphism of prtH gene from 5 strains of P.g in order to explore the relationship between P.g and periodontitis.</p><p><b>METHODS</b>Using PCR, the prtH was amplified and cloned into pGEM-T vector. To illustrate the prtH polymorphism among P.g strains, the genomic DNAs were extracted and screened by PCR with three pairs of specific primers, dot blot and Southern blot hybridization using the biotin-labeled prtH sequence as probe.</p><p><b>RESULTS</b>Recombinant DNA pGEM-T- prtH was verified by restriction endonuclease and sequence assay. Strain W 381 and ATCC 33277 showed the identical results in PCR and hybridization assays, whereas strain ATCC 49417 and 14-3-2 revealed individual hybridization patterns. Strain 47A-1 seemed even not to contain prtH gene.</p><p><b>CONCLUSIONS</b>Different prtH gene sequences exist in different P.g strains. This polymorphism may indicate various potential virulent effects during the infection and pathogenesis. Established PCR protocol is sensitive for identification of prtH gene.</p>

An alternative approach for screening active bam HI variants: overexpression in T-7 RNA polymerase based system.

The type II restriction endonuclease, Bam HI, has been overexpressed in E. coli by cloning the Bam HI gene in frame with an E. coli Ribosome Binding Site (RBS) under the T7 promoter of an E. coli expression vector pRSET A. The expression level of Bam HI endonuclease using this construct was found to be higher than that reported of the overexpressing clone pAEK14. Our overexpressing clone, pAABRw in BL21 cells in presence of Bam HI methylase in pMAP6 following induction with IPTG yields about 9.2 x 10(6) units per gram wet cell paste. In vivo activity of the recombinant endonuclease could be confirmed by the SOS induction assay in JH139 cells even in the absence of T7 polymerase and cognate Bam HI methylase because of leaky expression in E. coli. This provides an alternate way to screen the active endonuclease and its variants.

Isolation and identification of Adenovirus in hospitalized children, under five years, with acute respiratory disease, in Havana, Cuba

Nine Adenovirus (Ad) strains isolated in Cuba, from 128 nasopharingeal swab specimens of children below five years old, with acute respiratory diseases, during 1996 and 1997, were studied by restriction enzyme analysis of genomic DNA with two endonucleases BamH I and Sma I. All different fragment patterns were compared with the respective prototypes. The identified adenoviruses were Ad 1 (n=4), Ad 2 (n=1) and Ad 6 (n=4). Males were more frequently infected than females. The analysis of the occurrence of these Adenovirus strains of subgenus C revealed that Ad 1 and Ad 6 were the predominant serotypes in 1996 and in 1997, respectively

Diversity of genomic electropherotypes of naturally occurring equine herpesvirus 1 isolates in Argentina

The genomes of 10 equine herpesvirus 1 (EHV-1) strains isolated in Argentina from 1979 to 1991, and a Japanese HH1 reference strain were compared by restriction endonuclease analysis. Two restriction enzymes, Bam HI and Bgl II, were used and analysis of the electropherotypes did not show significant differences among isolates obtained from horses with different clinical signs. This suggests that the EHV-1 isolates studied, which circulated in Argentina for more than 10 years, belong to a single genotype

Location and rapid analysis of the intragenic BamHI polymorphic site of the factor IX gene

We report the precise location and a polymerase chain reaction (PCR)-based method for the analysis of the intragenic BamHI polymorphism of the factor IX (FIX) gene. After screening DNA samples from the Brazilian Black population by a selective amplification of a segment of the FIX gene containing entire exon 2, intron 2, and exon 3 followed by digestion of PCR products with BamHI, we were able to identify individuals presenting the polymorphic BamHI site. By DNA sequencing of selected samples, the dimorphic base was located at nucleotide number 6575 (intron 2). The PCR method outlined here allows rapid and easy analysis of this polymorphism. Its application may be particularly useful for carrier detection and prenatal diagnosis of hemophilia B in the Black population, thus far the only one that has been shown to be polymorphic for this site. Because of its apparent restrictive pattern it may also be used in combination with other markers for estimates of racial admixture in mixed populations in which the Black population is present (as is the case for most countries in the American continent).