Recent advances in CRISPR-related transposable elements / 生物工程学报

A new wave of research has been inspired by the CRISPR-Cas system with respect to their application in genome editing. The CRISPR-Cas system can not only be applied in gene knockout and insertion, but also be used in base editing, transcriptional regulation and recombination of gene clusters. However, the low efficiency of homology-directed repair (HDR) limits its application. Unlike the CRISPR-Cas system, mobile genetic elements (MGE) can insert DNA fragments into cell chromosomes without the aid of HDR. Recently, it is reported that CRISPR-related transposable elements can guide targeted DNA insertion. Their transposition mechanisms and reprogramming abilities have brought novel opportunities to the development of this field. This review summarized the research progress and application development of natural CRISPR-related transposable elements in recent years, as well as the applications of fused dCas9-transposase. It proposed the application prospects and potential challenges of CRISPR-related transposable elements in the future, which provided a reference for the development direction of gene editing tools.

A soil bacterial catabolic pathway on the move: Transfer of nicotine catabolic genes between Arthrobacter genus megaplasmids and invasion by mobile elements

The 165,137 bp plasmid pAO1 of Paenarthrobacter nicotinovorans carries the genes of a nicotine catabolicpathway. The genes are organized into several gene modules responsible for the catabolism of L- and D-nicotineto nicotine blue, a-ketoglutarate and succinate. Various modules of these genes have been shown to be presentin gram-positive (Gram?) soil bacteria. The presence of the identical pAO1 nic-genes on the 288,370 bpplasmid pZXY21 of Arthrobacter sp. ZXY2 (96% to 100% at the nucleotide level) permitted the identificationof the limits of this DNA fragment. At the 50 end of the nic-genes are located the ORFs of two predictedintegrases of the tyrosine recombinase family with conserved R, H, R and Y catalytic residues and that of asmall transposase with a predicted leucine zipper motive. They are related to Tn554A, Tn554B and Tn554C ofStaphylococcus aureus and suggest that the entire nic-genes DNA fragment represents a large catabolictransposon. Surprisingly the nic-genes on pZXY21 were found to be interspersed by mobile elements encodingtransposases of various IS families. Insertion of these IS elements disrupts nicotine degradation and divide thenic-genes DNA into potentially new transposons. This finding may illustrate how nicotine catabolic genes canbe mobilized and spread by horizontal gene transfer to other soil bacteria.

Chromosomal distribution of the retroelements Rex 1, Rex 3 and Rex 6 in species of the genus Harttia and Hypostomus (Siluriformes: Loricariidae)

The transposable elements (TE) have been widely applied as physical chromosome markers. However, in Loricariidae there are few physical mapping analyses of these elements. Considering the importance of transposable elements for chromosomal evolution and genome organization, this study conducted the physical chromosome mapping of retroelements (RTEs) Rex1, Rex3 and Rex6 in seven species of the genus Harttia and four species of the genus Hypostomus, aiming to better understand the organization and dynamics of genomes of Loricariidae species. The results showed an intense accumulation of RTEs Rex1, Rex3 and Rex6 and dispersed distribution in heterochromatic and euchromatic regions in the genomes of the species studied here. The presence of retroelements in some chromosomal regions suggests their participation in various chromosomal rearrangements. In addition, the intense accumulation of three retroelements in all species of Harttia and Hypostomus, especially in euchromatic regions, can indicate the participation of these elements in the diversification and evolution of these species through the molecular domestication by genomes of hosts, with these sequences being a co-option for new functions.(AU)

Os elementos transponíveis (TE) têm sido amplamente aplicados como marcadores cromossômicos. Contudo, em Loricariidae, há poucas análises de mapeamento físico destes elementos. Considerando a importância de elementos transponíveis para a evolução cromossômica e organização genômica, este trabalho realizou o mapeamento físico cromossômico dos retroelementos (RTEs) Rex1, Rex3 e Rex6 em sete espécies do gênero Harttia e em quatro espécies do gênero Hypostomus, com o intuito de melhor compreender a organização e dinâmica dos genomas das espécies de Loricariidae. Os resultados evidenciaram um intenso acúmulo dos RTEs Rex1, Rex3 e Rex6 e distribuição dispersa em regiões heterocromáticas e eucromáticas no genoma das espécies estudadas. A presença de retroelementos em algumas regiões cromossômicas sugere sua participação em vários rearranjos cromossômicos. Além disso, o intenso acúmulo dos três retroelementos em todas as espécies de Harttia e Hypostomus, especialmente em regiões eucromáticas, pode indicar a participação destes elementos na diversificação e evolução destas espécies através da domesticação molecular pelo genoma dos hospedeiros, com estas sequências sendo co-optadas paras novas funções.(AU)

Drosophila relics hobo and hobo-MITEs transposons as raw material for new regulatory networks

Abstract Hypermutable strains of Drosophila simulans have been studied for 20 years. Several mutants were isolated and characterized, some of which had phenotypes associated with alteration in development; for example, showing ectopic legs with eyes being expressed in place of antennae. The causal agent of this hypermutability is a non-autonomous hobo-related sequence (hoboVA). Around 100 mobilizable copies of this element are present in the D. simulans genome, and these are likely mobilized by the autonomous and canonical hobo element. We have shown that hoboVA has transcription factor binding sites for the developmental genes, hunchback and even-skipped, and that this transposon is expressed in embryos, following the patterns of these genes. We suggest that hobo and hobo-related elements can be material for the emergence of new regulatory networks.

Active miniature inverted-repeat transposable elements transposon in plants: a review / 生物工程学报

Miniature inverted-repeat transposable elements transposon is a special transposon that could transpose by "cut-paste" mechanism, which is one of characteristics of DNA transposons. Otherwise, the copy number of MITEs is very high, which is one of characteristics of RNA transposons. Many MITE families have been reported, but little about active MITEs. We summarize recent advances in studying active MITEs. Most the MITEs belong to the Tourist-like family, such as mPing, mGing, PhTourist1, Tmi1 and PhTst-3. Additionally, DTstu1 and MITE-39 belong to Stowaway-like family, and AhMITEs1 belongs to Mutator-like family. Moreover, we summarize the structure (terminal inverse repeats and target site duplications), copy number, evolution pattern and transposition characteristics of these active MITEs, to provide the foundation for the identification of other active MITEs and subsequent research on MITE transposition and amplification mechanism.

Foldback Intercoil DNA and the Mechanism of DNA Transposition

Foldback intercoil (FBI) DNA is formed by the folding back at one point of a non-helical parallel track of double-stranded DNA at as sharp as 180degrees and the intertwining of two double helixes within each other's major groove to form an intercoil with a diameter of 2.2 nm. FBI DNA has been suggested to mediate intra-molecular homologous recombination of a deletion and inversion. Inter-molecular homologous recombination, known as site-specific insertion, on the other hand, is mediated by the direct perpendicular approach of the FBI DNA tip, as the attP site, onto the target DNA, as the attB site. Transposition of DNA transposons involves the pairing of terminal inverted repeats and 5-7-bp tandem target duplication. FBI DNA configuration effectively explains simple as well as replicative transposition, along with the involvement of an enhancer element. The majority of diverse retrotransposable elements that employ a target site duplication mechanism is also suggested to follow the FBI DNA-mediated perpendicular insertion of the paired intercoil ends by non-homologous end-joining, together with gap filling. A genome-wide perspective of transposable elements in light of FBI DNA is discussed.

Transposable Elements and Genome Size Variations in Plants

Although the number of protein-coding genes is not highly variable between plant taxa, the DNA content in their genomes is highly variable, by as much as 2,056-fold from a 1C amount of 0.0648 pg to 132.5 pg. The mean 1C-value in plants is 2.4 pg, and genome size expansion/contraction is lineage-specific in plant taxonomy. Transposable element fractions in plant genomes are also variable, as low as ~3% in small genomes and as high as ~85% in large genomes, indicating that genome size is a linear function of transposable element content. Of the 2 classes of transposable elements, the dynamics of class 1 long terminal repeat (LTR) retrotransposons is a major contributor to the 1C value differences among plants. The activity of LTR retrotransposons is under the control of epigenetic suppressing mechanisms. Also, genome-purging mechanisms have been adopted to counter-balance the genome size amplification. With a wealth of information on whole-genome sequences in plant genomes, it was revealed that several genome-purging mechanisms have been employed, depending on plant taxa. Two genera, Lilium and Fritillaria, are known to have large genomes in angiosperms. There were twice times of concerted genome size evolutions in the family Liliaceae during the divergence of the current genera in Liliaceae. In addition to the LTR retrotransposons, non-LTR retrotransposons and satellite DNAs contributed to the huge genomes in the two genera by possible failure of genome counter-balancing mechanisms.

The Impact of Transposable Elements in Genome Evolution and Genetic Instability and Their Implications in Various Diseases

Approximately 45% of the human genome is comprised of transposable elements (TEs). Results from the Human Genome Project have emphasized the biological importance of TEs. Many studies have revealed that TEs are not simply "junk" DNA, but rather, they play various roles in processes, including genome evolution, gene expression regulation, genetic instability, and cancer disposition. The effects of TE insertion in the genome varies from negligible to disease conditions. For the past two decades, many studies have shown that TEs are the causative factors of various genetic disorders and cancer. TEs are a subject of interest worldwide, not only in terms of their clinical aspects but also in basic research, such as evolutionary tracking. Although active TEs contribute to genetic instability and disease states, non-long terminal repeat transposons are well studied, and their roles in these processes have been confirmed. In this review, we will give an overview of the importance of TEs in studying genome evolution and genetic instability, and we suggest that further in-depth studies on the mechanisms related to these phenomena will be useful for both evolutionary tracking and clinical diagnostics.

Characterization of pseudogenes in members of the order Frankineae.

Pseudogenes are defined as non-functional relatives of genes whose protein-coding abilities are lost and are no longer expressed within cells. They are an outcome of accumulation of mutations within a gene whose end product is not essential for survival. Proper investigation of the procedure of pseudogenization is relevant for estimating occurrence of duplications in genomes. Frankineae houses an interesting group of microorganisms, carving a niche in the microbial world. This study was undertaken with the objective of determining the abundance of pseudogenes, understanding strength of purifying selection, investigating evidence of pseudogene expression, and analysing their molecular nature, their origin, evolution and deterioration patterns amongst domain families. Investigation revealed the occurrence of 956 core pFAM families sharing common characteristics indicating co-evolution. WD40, Rve_3, DDE_Tnp_IS240 and phage integrase core domains are larger families, having more pseudogenes, signifying a probability of harmful foreign genes being disabled within transposable elements. High selective pressure depicted that gene families rapidly duplicating and evolving undoubtedly facilitated creation of a number of pseudogenes in Frankineae. Codon usage analysis between protein-coding genes and pseudogenes indicated a wide degree of variation with respect to different factors. Moreover, the majority of pseudogenes were under the effect of purifying selection. Frankineae pseudogenes were under stronger selective constraints, indicating that they were functional for a very long time and became pseudogenes abruptly. The origin and deterioration of pseudogenes has been attributed to selection and mutational pressure acting upon sequences for adapting to stressed soil environments.

Hidden magicians of genome evolution.

Transposable elements (TEs) represent genome’s dynamic component, causing mutations and genetic variations. Transposable elements can invade eukaryotic genomes in a short span; these are silenced by homology-dependent gene silencing and some functional parts of silenced elements are utilized to perform novel cellular functions. However, during the past two decades, major interest has been focused on the positive contribution of these elements in the evolution of genomes. The interaction between mobile DNAs and their host genomes are quite diverse, ranging from modifications of gene structure to alterations in general genome architecture and can be regarded as hidden magicians in shaping evolution of genomes. Some of the prominent examples that impressively demonstrate the beneficial impact of TEs on host biology over evolutionary time include their role in structure and functions of eukaryotic genomes.

IS CR1 asociado con genes blaCTX-M-1 y bla CTX-M-2 en plásmidos IncN e IncFIIA aislados en Klebsiella pneumoniae de origen hospitalario en Mérida, Venezuela / IS CR1 associated with bla CTX-M-1 y bla CTX-M-2 genes in IncN and IncFIIA plasmids isolated from Klebsiella pneumoniae of nosocomial origin in Mérida, Venezuela

Introducción. Las secuencias de inserción tales como IS CR1 promueven la captura, transposición y expresión de los genes bla CTX-M, facilitando, de esta manera, su diseminación rápida en la población bacteriana. Objetivo. Se determinó la presencia del elemento IS CR1 y su asociación con genes bla CTX-M-1 y bla CTX-M-2 en plásmidos de diferentes grupos de incompatibilidad en Klebsiella pneumoniae de origen hospitalario. Materiales y métodos. Se aislaron tres cepas de K. pneumoniae con sensibilidad disminuida a cefalosporinas de amplio espectro, de neonatos con septicemia hospitalaria. La presencia de β -lactamasas de espectro expandido (BLEE) fue determinada fenotípicamente. Los plásmidos se aislaron y clasificaron según grupos de incompatibilidad por tipificación del replicón por reacción en cadena de la polimerasa (PCR). Los genes bla BLEE y su asociación a IS CR1 se determinaron por PCR y secuenciación directa, usando varios juegos de iniciadores. Resultados. Todas las cepas demostraron un perfil fenotípico indicativo de producción de BLEE, transferibles por conjugación. Los ensayos de PCR para para cefotaximasas (CTX-M) y el análisis de la secuenciación, revelaron que las cepas portaban genes bla CTX-M-1 y bla CTX-M-2. Estos genes se encontraron en plásmidos conjugados de 150 kb, aproximadamente, relacionados con los grupos IncN e IncFIIA, respectivamente. IS CR1 se encontró ´aguas arriba´ ( upstream ) y asociado con los genes bla CTX-M-1 y bla CTX-M-2. Conclusión. Este es el primer reporte realizado en Venezuela donde la presencia de IS CR1 está estrechamente asociada con la movilización de los genes bla CTX-M-1 y bla CTX-M-2 en plásmidos conjugativos IncN y IncFIIA en cepas de K. pneumoniae que circulan en una Unidad de Alto Riesgo Neonatal.

Introduction: Insertion sequences such as IS CR1 promote capture, transposition and expression of bla CTX-M genes. Thus, gene dissemination in bacterial populations occurs rapidly. Objective: To determine the presence of IS CR1 sequence genes and their association with bla CTX-M-1 and bla CTX-M-2 on plasmids IncN and IncFIIA from K. pneumoniae of nosocomial origin, was determined. Materials and methods: Three strains of K. pneumoniae with reduced susceptibility to extendedspectrum cephalosporins were isolated from neonatal sepsis cases of nosocomial origin. Phenotypic tests showed the presence of ESBLs. Plasmids were isolated and classified according to incompatibility groups by PCR replicon typing. Detection and association of IS CR1 with bla CTX-M genes were determined by PCR and direct sequencing through the use of several sets of PCR primers. Results: All strains showed phenotypic profile consistent with ESBL-producing transferred by conjugation. PCR amplification assay for CTX-M together with sequencing analysis revealed that strains carrying bla CTX-M-1 y bla CTX-M-2 genes were localized in plasmids of approximately 150 kb related to IncN and IncFIIA groups, respectively. IS CR1 was found upstream and associated with bla CTX-M-1 y bla CTX-M-2 genes. Conclusion. Thus far, this is the first Venezuelan report, in which IS CR1 presence is closely related to bla CTX-M-1 y bla CTX-M-2 gene mobilization in IncN and IncFIIA conjugative plasmids located in K. pneumonaiae strains circulating at a neonatal high risk unit.

Transposable Elements: No More 'Junk DNA'

Since the advent of whole-genome sequencing, transposable elements (TEs), just thought to be 'junk' DNA, have been noticed because of their numerous copies in various eukaryotic genomes. Many studies about TEs have been conducted to discover their functions in their host genomes. Based on the results of those studies, it has been generally accepted that they have a function to cause genomic and genetic variations. However, their infinite functions are not fully elucidated. Through various mechanisms, including de novo TE insertions, TE insertion-mediated deletions, and recombination events, they manipulate their host genomes. In this review, we focus on Alu, L1, human endogenous retrovirus, and short interspersed element/variable number of tandem repeats/Alu (SVA) elements and discuss how they have affected primate genomes, especially the human and chimpanzee genomes, since their divergence.

Long-term and stable expression of transgene mediated by piggyBac transposon in gynecological malignant tumor cells / 中华妇产科杂志

Objective To investigate the expression of exogenous gene transferred by piggyBac (PB) transposon in various gynecological malignant cell lines and reveal its potential application of gene therapy in gynecological cancer.Methods Amplified herpes simplex virus thymidine kinase (HSV-tk) gene coding region by PCR and integrated it into PB expression vector, PB[Act-RFP]DS, for reconstructing PB[Act-RFP, HSV-tk]DS (pPB/TK).By using different transfection reagents: FuGENE HD, jetPEI, lipofectamine 2000, pPB/TK together with helper plasmid Act-PBase were cotransfected into four mostly common gynecological malignant tumor cell lines HeLa, JEG-3, SKOV3 and HEC-1B.The mRFP1 report gene expressions was observed and detected by fluorescence microscope and flow cytometry to analyze transfection efficiency.The expressions of HSV-tk and mRFP1 gene were detected by reverse transcription PCR (RT-PCR).The cytotoxic effect of various concentration of pro-drug ganciclovir (GCV) for transfected cells was detected by methyl thiazole tetrazolium assay.The transfected cells were positive sorted by flow cytometry and limiting diluted to obtain the stable transfected cell line.The insertion sites of foreign gene tranferred by PB transposon in genome were analyzed by inverse PCR.Results (1) Double digests analysis and sequences test demonstrated that pPB/TK vector was reconstructed successfully.(2) Using three different transfective reagents, PB trausposon transferred HSV-tk gene and mRFP1 gene into HeLa, HEC-1 B, SKOV3 and JEG-3 cell efficiently, and the transfection efficiency of pPB/TK for the same cell was different by using different transfective reagents; in Hela cell, the transfection efficiency of FuGENE HD [(78.7 ± 9.2) %]was higher than that of lipofectamine 2000 [(54.1 ± 11.4) %]and jetPEI [(46.5 ± 7.4) %, all P < 0.05] ; using the same transfective reagent, the transfection efficiency of pPB/TK was also different on various cell lines, using FuGENE HD, the transfeetion efficiency of pPB/TK on HeLa, JEG-3 and SKOV3 cell was (78.7 ± 9.2) %, (74.4 ± 8.9) % and (83.2 ± 9.7) % respectively, which all were higher than that on HEC-1B [(39.5 ± 8.7) %, P < 0.05] .(3) RT-PCR showed that there were the mRNA expression of HSV-tk and mRFP1 in all cell lines.(4) 50% inhibitory concentration of GCV for transfected cells, HeLa, JEG-3, SKOV3 and HEC-1B, was 1.29, 3.35, 0.09 and 13.28 μg/ml respectively.Inhibitory effect of GCV (10 μg/ml) on SKOV3 transfected with pPB/TK was (86 ± 9) %, which was superior to that transfected with pORF-HSVtk alone [(52 ± 12)%, P < 0.05] .(5) The insertion sites of PB transposon in the target cells genome were located at TTAA sites, mRFP1 expression still could be detected in three months after transfected.Conclusions PB transposon could transfer exogenous gene into various gynecological malignant cells, which could integrated into genome and obtain a long-term and stable expression.It is expected that PB transposon may supply a more efficient and safer transgene technology platform for gene therapy in gynecological cancer.

Boty-II, a novel LTR retrotransposon in Botrytis cinerea B05.10 revealed by genomic sequence

Botrytis cinerea is a necrotrophic pathogen causing pre- and post-harvest diseases in at least 235 plant species. It manifests extraordinary genotype and phenotype variation. One of the causes of this variation is transposable elements. Two transposable elements have been discovered in this fungus, the retrotransposon (Boty), and the transposon (Flipper). In this work, two complete (Boty-II-76 and Boty-II-103) and two partial (Boty-II-95 and Boty-II-141) long terminal repeat (LTR) retrotransposons were identified by an in silico genomic sequence analysis. Boty-II-76 and Boty-II-103 contain 6439 bp nucleotides with a pair of LTRs at both ends, and an internal deduced pol gene encoding a polyprotein with reverse transcriptase and DDE integrase domains. They are flanked by 5 bp direct repeats (ACCAT, CTTTC). In Boty-II-141, two LTRs at both ends, and a partial internal pol gene encoding a protein with a DDE integrase domain were identified. In Boty-II-95, a right LTR and a partial internal pol gene encoding a protein with no conserved domains were identified. Boty-II uses a self-priming mechanism to initiate synthesis of reverse transcripts. The sequence of the presumed primer binding site for first-strand reverse transcription is 5’-TTGTACCAT-3’. The polypurine-rich sequence for plus-strand DNA synthesis is 5’-GCCTTGAGCGGGGGGTAC-3’. Fourteen Boty-II LTRs that contain 125-158 bp nucleotides and share 69.1 ~ 100 percent identities with the short inverted terminal repeats of 5 bp (TGTCA…TGACA) were discovered. Analysis of structural features and phylogeny revealed that Boty-II is a novel LTR retrotransposon. It could potentially be used as a novel molecular marker for the investigation of genetic variation in B. cinerea.

Locus-specific analysis of IS100 insertion within Yersinia pestis genome / 中国地方病学杂志

Objective To study the genotyping distribution of the Yersinia pestis(Y.pestis)strains by characterizing the diversity of the insertion sequence IS100 within the Y.pestis genome.Methods Derived fromthe known sequence of oriental strain CO92,5 pairs of locus-specific primers originating from both sides of the adjacent region of IS100 copies were designed,and two other complementary primers inside the IS100 sequence were designed to correspond with the outer primers.Then,91 Y.pestis strains and l pseudotubebculosis strain were tested by the specific PCR method using the primers described above and the PCR products were conformed by the sequence analysis,then further analysis WaS performed after the IS100 status was marked on the map of the plague focus type of china.Results The 91 Y.pestis strains had different IS100 status in their genome on tested loci.some possessed IS100 insertion,some didn't,and others changed their genome constitution.The IS100 possession on the 5 loci also suggested a distribution of regionality.Conclusion The analysis of some IS100 insertion element loci reveals that the IS100 genotyping distribution is consistent with the plague focus of type of China.And IS100genotyping pattern of the Y.pestis stains well reflects its genome constitution and the high flowability in its natural evolution.

Bacteria resistance surveillance on Enterococci Isolated from pedlatric hospitals and distribution of resistance genes ermB,mefA,tetM and the integrase gene intTn of Tn1545 in Enterococci / 中华检验医学杂志

Objective To determine the drug-resistance rate of Enterococci isolated from patients of 5 padiatric hospitals located at different areas in China,and to investigate the distribution of resistance genes ermB,mefA,tetM and the integrase gene intTn of Tn1545 in Enterococci.Methods The antimicrobial susceptibility to 8 antibiotics of 2 216 Enteroeocei isolates was determined.PCR was used to detect the macrolide resistance genes ermB and mefA,tetracycline resistance genes tetM,and the integrase gene int-Tn of Tn1545.Results The resistance rates to erythromycin,ampicillin,gentamicin and teicoplanin were 86.5%,48.0%,60.5% and 0.7%,respectively.All isolated Enterococci straim were found sensitive to vancomycin.Of the detected 225 strains,70.7% of the 225 detected strains carried ermB gene while 75.1% of them carried tetracycline resistance gene tetM:only one strain had mefA.The presence of ermB gene in erythromycin MIC＞256 mg/L straim group(95.7%)strains was higher than those in erythromycin MIC＜256 mg/L group(2.5%).The int-Tn gene was detected in 40.9%(92/225)of the 225 test strains.The presence of ermB gene in int-Tn positive group strains was higher(84.8%)than those in int-Tn negative strains group(60.9%).So did the tetM in int-Tn positive group(83.7%)compared with those in int-Tn negative group(70.0%).Conclusions Enterococci sbowed a high resistance rate to the antibiotics we monitored,especially to erythromycin;but still very senstive to glycopeptide antibiotics. Resistance to macrolide in Enterococci collected from clinical in five Children's Hospital was generally mediated by methylation of 23S rRNA via ermB methylase. Enterococci resistance to tetracycline was predominantly due to ribosomal protection encoded by tetM. There was a strong relationship of the ermB and tetM genes with Tn1545-related elements.

Structures of resistance transposons and multilocus sequencing typing in vancomycin-resistant enterococci strains isolated from five hospitals in Hangzhou / 中华检验医学杂志

Objective To determine the structures of resistance transposons and muhilocus sequencing typing(MLST)in the vancomycin resistant enterococcus(VRE).Methods Twenty-one VRE strains were isolated from five hospitals in Hangzhou.The resistance to antimicrobial agents was determined by Etest.Polymerase chain reaction(PCR),conjugation,plasmid extract,transposon structures,pulse field gel electrophoresis(PFGE),muhilocus sequencing typing(MLST),and multiple-locus variable-number tandem repeat analysis(MLVA)were carried out.Results All of the 21 VRE strains harbored the vanA gene.These strains were divided into 10 PFGE types,7 sequence types(STs)and 5 MLVA types.All of these VRE strains were susceptible to linezolid and tigecycline.The vanA genes in two VRE strains were located in transposon Tnl546,and those in the other 19 VRE strains were located in transpeson Tnl546- like,with ISl485 inserted in vanXY.Vancomycin resistance of 1 8 VRE isolates was transferred by filter mating. All of these conjugants had a plasmid containing a molecular size of about 54 000 bo.Conclusions These 21 VRE strains were all caused by the vanA gene and divided into 7 MIST types.A novel trasnposon was detected.Most of these VRE isolates belonged to the clonal complex(CC17)by MIST,which was the hospital-adapted and pandemic VRE clonal complex.