genome integration

基因组整合
  • 文章类型: Journal Article
    随着人类祖细胞分化为神经元,许多基因的活动发生变化;这些变化保持在一个狭窄的范围内,称为基因组稳态。这个过程,这改变了整个表达基因组的同步,在精神分裂症等神经发育疾病中被扭曲。通过改变基因集形成的协调基因活动网络包括重复的协调模块,受核FGFR1的熵控制作用支配,已知与DNA拓扑相关。这些模块可以建模为能量转移电路,揭示了通过减少基因活性中的振荡(噪声)来维持基因组稳态,同时允许基因活性变化通过网络传播;这在神经元定向细胞中比在神经祖细胞中更容易发生。这些发现提出了一个“纠缠”全球基因组的模型,响应发育信号的协调稳态系统,由核FGFR1控制,并在疾病中重新编程。
    As human progenitor cells differentiate into neurons, the activities of many genes change; these changes are maintained within a narrow range, referred to as genome homeostasis. This process, which alters the synchronization of the entire expressed genome, is distorted in neurodevelopmental diseases such as schizophrenia. The coordinated gene activity networks formed by altering sets of genes comprise recurring coordination modules, governed by the entropy-controlling action of nuclear FGFR1, known to be associated with DNA topology. These modules can be modeled as energy-transferring circuits, revealing that genome homeostasis is maintained by reducing oscillations (noise) in gene activity while allowing gene activity changes to be transmitted across networks; this occurs more readily in neuronal committed cells than in neural progenitors. These findings advance a model of an \"entangled\" global genome acting as a flexible, coordinated homeostatic system that responds to developmental signals, is governed by nuclear FGFR1, and is reprogrammed in disease.
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  • 文章类型: Journal Article
    D-泛酸,作为一种重要的维生素,广泛应用于饲料,医学,化妆品等领域。然而,目前通过微生物发酵生产D-泛酸仍然存在局限性。在本文中,我们通过阻断有机酸途径构建了D-泛酸生产的重组菌株,促进丙酮酸生物合成,缓解乙酰乳酸合酶的反馈抑制,提高葡萄糖摄入能力,并修改代谢途径中的必需基因。此外,获得了由ilvC编码的来自大肠杆菌(EcAHAIR)的新乙酰乳酸异还原酶突变体V412A,以探索其底物混杂性。与野生型相比,变体EcAHAIR-V412A具有减少的空间位阻和增强的分子间力,导致对2-乙酰乳酸的高亲和力。最终,最终菌株DPAN19/trc-ilvCV412A的发酵产量达到4.65g/L,在摇瓶培养中与DPA8菌株相比增加了192.5%,并在5L生物反应器中产生了62.82g/L的D-泛酸。本文所述的代谢工程策略和酶修饰方法为D-泛酸的生物制造提供了一个特殊的视角,支链氨基酸及其衍生物。
    D-Pantothenic acid, as a momentous vitamin, is extensively applied to feed, medicine, cosmetics and other fields. However, there are still limitations to produce D-pantothenic acid by microbial fermentation at present. In this paper, we constructed a recombinant strain for D-pantothenic acid production by blocking the organic acid pathway, boosting pyruvate biosynthesis, relieving feedback inhibition of acetolactate synthase, improving glucose intake capacity, and modifying essential genes in the metabolic pathway. In addition, a new acetolactate isomeroreductase mutant V412A origin from Escherichia coli (EcAHAIR) encoded by ilvC was obtained to explore its substrate promiscuity. Compared with the wild type, the variant EcAHAIR-V412A has reduced steric hindrance and enhanced intermolecular forces, resulting in a high affinity for 2-acetolactate. Eventually, the fermentation production of the final strain DPAN19/trc-ilvCV412A reached 4.65 g/L, increased by 192.5% compared with strain DPA8 in shake flask cultivation and produced 62.82 g/L D-pantothenic acid in a 5 L bioreactor. The metabolic engineering strategies and enzyme modification approaches described in this paper provide a particular perspective for the bio-manufacturing of D-pantothenic acid, branched-chain amino acids and its derivates.
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  • 文章类型: Journal Article
    阴茎癌(PC)是一种罕见的男性恶性肿瘤,伴早期淋巴结转移,预后差。人乳头瘤病毒(HPV)在PC的癌变中起关键作用。这篇综述旨在总结HPV感染与PC之间在病毒-宿主基因组整合模式(HPV和PC基因组中的破坏区域)方面的关联。遗传改变,和表观遗传调控(甲基化和microRNA修饰)发生在HPV和PCDNA,以及肿瘤免疫微环境重编程。此外,讨论了HPV疫苗接种策略在PC预防和治疗中的潜力.了解HPV相关的多维机制和HPV疫苗的应用将促进PC的合理和新颖管理。
    Penile cancer (PC) is a rare male malignant tumor, with early lymph node metastasis and poor prognosis. Human papillomavirus (HPV) plays a key role in the carcinogenesis of PC. This review aims to summarize the association between HPV infection and PC in terms of virus-host genome integration patterns (the disrupted regions in the HPV and PC genome), genetic alterations, and epigenetic regulation (methylation and microRNA modification) occurring in HPV and PC DNA, as well as tumor immune microenvironment reprogramming. In addition, the potential of HPV vaccination strategies for PC prevention and treatment is discussed. Understanding of the HPV-related multidimensional mechanisms and the application of HPV vaccines will promote rational and novel management of PC.
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  • 文章类型: Preprint
    非病毒DNA供体模板已广泛用于通过同源重组(HR)的靶向基因组整合。使用RNA引导的核酸内切酶编辑器系统(如CRISPR/Cas9),该过程变得更有效。环状单链DNA(cssDNA)先前已被用作基因组工程催化剂(GATALYST),用于有效且安全的靶向基因敲入。在这里我们开发了enGager,具有增强的GATALYST相关基因组编辑器的系统,包括一组新的基因组编辑器,其中通过将cssDNA直接连接到与ssDNA结合肽融合的核定位的Cas9来提高环状单链(css)供体DNA的整合效率。在多个细胞系中的多个基因组基因座处观察到编码GFP的敲入DNA的定点基因组整合和表达的改善。集成效率的提高,与未融合的Cas9编辑相比,范围从1.5倍到6倍以上,对于原代细胞中长度>4Kb的转基因,增强最为明显。enGager增强的基因组整合更喜欢ssDNA供体,与传统的dsDNA供体不同,使用与优化的cssDNA结合肽融合的enGager,异常高效,在33%的原代人T细胞中实现了嵌合抗原受体(CAR)转基因的靶向整合。这些CAR-T原代细胞的增强的抗肿瘤功能证明了转基因的功能能力。“具有ssDNA优化基因组工程的三方编辑器”(TESOGENASETM)系统有助于解决治疗性基因修饰的功效需求,同时避免了目前用于CAR-T工程的病毒载体的安全性和有效载荷大小限制。
    Non-viral DNA donor template has been widely used for targeted genomic integration by homologous recombination (HR). This process has become more efficient with RNA guided endonuclease editor system such as CRISPR/Cas9. Circular single stranded DNA (cssDNA) has been harnessed previously as a genome engineering catalyst (GATALYST) for efficient and safe targeted gene knock-in. Here we developed enGager, a system with enhanced GATALYST associated genome editor, comprising a set of novel genome editors in which the integration efficiency of a circular single-stranded (css) donor DNA is elevated by directly tethering of the cssDNA to a nuclear-localized Cas9 fused with ssDNA binding peptides. Improvements in site-directed genomic integration and expression of a knocked-in DNA encoding GFP were observed at multiple genomic loci in multiple cell lines. The enhancement of integration efficiency, compared to unfused Cas9 editors, ranges from 1.5- to more than 6-fold, with the enhancement most pronounced for transgenes of > 4Kb in length in primary cells. enGager-enhanced genome integration prefers ssDNA donors which, unlike traditional dsDNA donors, are not concatemerized or rearranged prior to and during integration Using an enGager fused to an optimized cssDNA binding peptide, exceptionally efficient, targeted integration of the chimeric antigen receptor (CAR) transgene was achieved in 33% of primary human T cells. Enhanced anti-tumor function of these CAR-T primary cells demonstrated the functional competence of the transgenes. The \'tripartite editors with ssDNA optimized genome engineering\' (TESOGENASE™) systems help address the efficacy needs for therapeutic gene modification while avoiding the safety and payload size limitations of viral vectors currently used for CAR-T engineering.
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  • 文章类型: Journal Article
    马类肉瘤(EqS)是与牛乳头瘤病毒1和2(BPV-1和-2)相关的成纤维细胞来源的皮肤肿瘤。根据南方印迹,未发现BPV-1基因组整合在宿主细胞基因组中,这表明EqS发病机制不是插入诱变的结果。因此,CRISPR/Cas9暗示了一种用于选择性靶向BPV-1游离体或遗传锚定的可疑宿主因子的有趣工具。为了在概念验证研究中解决这个问题,我们使用靶向基因座扩增(TLA)证实了EqS中BPV-1的专有附加型持久性。为了研究CRISPR/Cas9介导的BPV-1游离体编辑,建立并表征了原代马成纤维细胞培养物。在EqS成纤维细胞培养中,CRISPR介导的游离E5和E6癌基因以及BPV-1长控制区的靶向是成功的,并导致BPV-1负荷的显着减少。此外,马波形蛋白(VIM)的缺失,在EqS中高度表达,显著减少了BPV-1游离体的数量。我们的结果表明,基于CRISPR/Cas9的基因靶向可以作为一种工具,帮助进一步解开EqS发病机理的生物学。
    Equine sarcoids (EqS) are fibroblast-derived skin tumors associated with bovine papillomavirus 1 and 2 (BPV-1 and -2). Based on Southern blotting, the BPV-1 genome was not found to be integrated in the host cell genome, suggesting that EqS pathogenesis does not result from insertional mutagenesis. Hence, CRISPR/Cas9 implies an interesting tool for selectively targeting BPV-1 episomes or genetically anchored suspected host factors. To address this in a proof-of-concept study, we confirmed the exclusive episomal persistence of BPV-1 in EqS using targeted locus amplification (TLA). To investigate the CRISPR/Cas9-mediated editing of BPV-1 episomes, primary equine fibroblast cultures were established and characterized. In the EqS fibroblast cultures, CRISPR-mediated targeting of the episomal E5 and E6 oncogenes as well as the BPV-1 long control region was successful and resulted in a pronounced reduction of the BPV-1 load. Moreover, the deletion of the equine Vimentin (VIM), which is highly expressed in EqS, considerably decreased the number of BPV-1 episomes. Our results suggest CRISPR/Cas9-based gene targeting may serve as a tool to help further unravel the biology of EqS pathogenesis.
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  • 文章类型: Journal Article
    在密西西比州(2020-2022年)的棉花卷叶矮病毒种群表征过程中产生的基于Illumina的高通量测序数据的分析始终产生大小不同的重叠群(最常见的是4至7kb),具有相同的核苷酸含量,并且与现有植物副反转录病毒(Caulimoviridiae家族)编码的逆转录酶(RTases)具有相似性。最初的数据促使人们进行了深入研究,涉及分子和生物信息学方法,以表征这些菜刀类序列的性质和起源。因此,在这里,我们报告了与Caulimoviridae家族现有成员相关的内源性病毒元件(EVE),整合到陆地棉(陆地棉)的基因组中,为此,我们提出了临时名称“内源性棉花病毒因子”(eCPRVE)。我们的研究在A04染色体上确定了一个约15kbp长的基因座,该基因座由位于正和负义DNA链(eCPRVE和eCPRVE-)上的头对头定向串联拷贝组成。eCPRVE+的序列包含几乎完整和轻微衰减的基因组信息,包括编码病毒运动蛋白(MP)的ORF,外壳蛋白(CP),RTase,和反式激活因子/病毒质蛋白(TA)。主要病毒蛋白的系统发育分析表明,eCPRVE最初可能源自属于该家族中推定的新属的同源病毒的基因组。出乎意料的是,在新识别的物种G.ekmanianum中还检测到由两个eCPRVE拷贝组成的相同的15kb长的基因座,揭示了棉花家族中相对较新的进化。
    Analyses of Illumina-based high-throughput sequencing data generated during characterization of the cotton leafroll dwarf virus population in Mississippi (2020-2022) consistently yielded contigs varying in size (most frequently from 4 to 7 kb) with identical nucleotide content and sharing similarities with reverse transcriptases (RTases) encoded by extant plant pararetroviruses (family Caulimoviridiae). Initial data prompted an in-depth study involving molecular and bioinformatic approaches to characterize the nature and origins of these caulimovirid-like sequences. As a result, here, we report on endogenous viral elements (EVEs) related to extant members of the family Caulimoviridae, integrated into a genome of upland cotton (Gossypium hirsutum), for which we propose the provisional name \"endogenous cotton pararetroviral elements\" (eCPRVE). Our investigations pinpointed a ~15 kbp-long locus on the A04 chromosome consisting of head-to-head orientated tandem copies located on positive- and negative-sense DNA strands (eCPRVE+ and eCPRVE-). Sequences of the eCPRVE+ comprised nearly complete and slightly decayed genome information, including ORFs coding for the viral movement protein (MP), coat protein (CP), RTase, and transactivator/viroplasm protein (TA). Phylogenetic analyses of major viral proteins suggest that the eCPRVE+ may have been initially derived from a genome of a cognate virus belonging to a putative new genus within the family. Unexpectedly, an identical 15 kb-long locus composed of two eCPRVE copies was also detected in a newly recognized species G. ekmanianum, shedding some light on the relatively recent evolution within the cotton family.
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  • 文章类型: Journal Article
    翼状胬肉是眼科最常见的病理之一,是良性的,纤维血管组织的过度生长,通常具有机翼状的外观,从角膜上的结膜。它由上皮和高度血管组成,上皮下,疏松的结缔组织。关于翼状胬肉的发病机制有很多争论,已经提出了许多理论,包括遗传不稳定性,细胞增殖,炎症影响,结缔组织退化,血管生成,异常细胞凋亡和病毒感染。目前,人乳头瘤病毒(HPV)参与翼状胬肉的发生是有争议的,据报道,58%的病例中存在HPV,而其他人未能在翼状胬肉中检测到HPV。在这项研究中,我们评估了翼状突和健康结膜样本中HPVDNA的存在和病毒基因型,和病毒整合到细胞基因组中。通过聚合酶链反应分析了40个原发性翼状组织样本和12个健康的结膜样本是否存在HPVDNA,使用MY09/MY11引物检测HPV-L1基因。通过该扩增子的DNA序列分析鉴定病毒基因型。通过蛋白质印迹检测HPV-L1衣壳蛋白分析HPV整合到细胞基因组中。在40个翼状组织样品中的19个中观察到HPV的存在。相比之下,健康结膜样本为阴性.要确定病毒类型,进行序列分析。有趣的是,19例翼状胬肉样本中有11例被鉴定为HPV-11型,同时,其余8例翼状胬肉标本被鉴定为HPV-18.HPV-L1衣壳蛋白仅在所研究的10个样品中的3个中发现。总之,我们的研究确定了翼状胬肉样本中仅存在HPVDNA,并描述了HPV-11和-18基因型.我们的结果表明,HPV可能参与了翼状胬肉的发病机制。另一方面,L1-HPV蛋白的表达提示病毒整合到细胞基因组中.
    Pterygium is one of the most frequent pathologies in ophthalmology, and is a benign, overgrowth of fibrovascular tissue, often with a wing-like appearance, from the conjunctiva over the cornea. It is composed of an epithelium and highly vascular, sub-epithelial, loose connective tissue. There is much debate surround the pathogenesis of pterygium and a number of theories have been put forward including genetic instability, cellular proliferation, inflammatory influence, and degeneration of connective tissue, angiogenesis, aberrant apoptosis and viral infection. At present, the involvement of human papillomavirus (HPV) in the genesis of pterygium is controversial, as have reported that HPV is present in 58% of cases, while others have failed to detect HPV in pterygium. In this study, we evaluated the presence and viral genotype of HPV DNA in pterygia and healthy conjunctiva sample, and virus integration into the cellular genome. Forty primary pterygia samples and 12 healthy conjunctiva samples were analyzed to HPV DNA presence by polymerase chain reaction, using MY09/MY11 primers of HPV-L1 gene. Viral genotype was identified by DNA sequence analysis of this amplicon. HPV integration into the cellular genome was analyzed by western blot detecting HPV-L1 capsid protein. Presence of HPV was observed in 19 of the 40 pterygia samples. In contrast, healthy conjunctiva samples were negative. To determine virus type, sequence analyses were performed. Interestingly, 11 out of the 19-pterygium samples were identified as HPV-11 type, meanwhile, the remaining 8 pterygium samples were identified as HPV-18. HPV-L1 capsid protein were found only in 3 out of the 10 samples studied. In conclusion, our study identified the presence of HPV DNA exclusively in pterygium samples and described HPV-11 and -18 genotypes. Our results suggest that HPV may be involved in the pathogenesis of pterygium. On the other hand, the expression of the L1-HPV protein suggests viral integration into the cellular genome.
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  • 文章类型: Journal Article
    为了加快呼吸系统疾病的药物靶标发现和验证,我们开发了一种通过AAV6介导的CRISPR-Cas9传递在鼠肺上皮细胞中原位体细胞基因破坏的优化方法。在评估单或双引导AAV载体形式后,在II型肺肺泡上皮细胞和远端气道细胞中观察到有效的基因编辑。Cas9变体,和具有组合指导RNA表达盒的顺序给药策略。特别是,在Cas9转基因动物中,我们能够证明不同上皮细胞类型中不同靶标的全群体基因破坏,最小到没有相关的炎症。我们还观察并表征了在肺细胞中发生的定向双链DNA断裂位点内的AAV载体整合事件。突出了AAV介导的DNA核酸酶递送的复杂因素。一起来看,我们展示了一种独特有效的小鼠肺躯体工程方法,这将极大地促进疾病的建模和治疗干预。
    With the aim of expediting drug target discovery and validation for respiratory diseases, we developed an optimized method for in situ somatic gene disruption in murine lung epithelial cells via AAV6-mediated CRISPR-Cas9 delivery. Efficient gene editing was observed in lung type II alveolar epithelial cells and distal airway cells following assessment of single- or dual-guide AAV vector formats, Cas9 variants, and a sequential dosing strategy with combinatorial guide RNA expression cassettes. In particular, we were able to demonstrate population-wide gene disruption within distinct epithelial cell types for separate targets in Cas9 transgenic animals, with minimal to no associated inflammation. We also observed and characterized AAV vector integration events that occurred within directed double-stranded DNA break sites in lung cells, highlighting a complicating factor with AAV-mediated delivery of DNA nucleases. Taken together, we demonstrate a uniquely effective approach for somatic engineering of the murine lung, which will greatly facilitate the modeling of disease and therapeutic intervention.
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  • 文章类型: Journal Article
    摄入诸如卷心菜的十字花科蔬菜与许多健康益处相关。芸苔属的主要防御化合物是氨基酸衍生的芥子油苷,它们与健康促进作用有关。这引发了建立生产芥子油苷的微生物细胞工厂作为稳定和可靠来源的愿望。这里,我们首次使用两种不同的工程策略在酿酒酵母中建立了苯丙氨酸衍生的苄基芥子油苷(BGLS)的生产:稳定的基因组整合与基于质粒的生物合成基因导入。尽管质粒工程菌株显示出在生物合成途径中每个基因(CYP83B1除外)的表达水平较高的趋势,与质粒工程化菌株相比,基因组工程化菌株产生的BGLS产量高8.4倍。此外,我们通过过表达进入点基因CYP79A2和CYP83B1优化了基因组工程菌株,导致BGLS产量增加2倍,但最后一种中间体硫苄基葡萄糖苷(dsBGLS)的水平也增加了4.8倍.我们在通过磺基转移酶将dsBGLS转化为BGLS的步骤中应用了几种方法来缓解代谢瓶颈,SOT16依赖于3'-磷酸腺苷-5'-磷酸硫酸盐(PAPS)。BGLS产量通过过表达SOT16增加1.7倍,通过引入APS激酶增加1.7倍,APK1,从拟南芥中介入PAPS再生轮回。通过过表达MET3和MET14调节内源性硫同化途径导致BGLS产生2.4倍至12.81μmol/L(=5.2mg/L)。重要性摄入诸如卷心菜的十字花科蔬菜与许多健康益处相关。芸苔属的主要防御化合物是氨基酸衍生的芥子油苷,它们与健康促进作用有关。这引发了建立生产芥子油苷的微生物细胞工厂作为稳定和可靠来源的愿望。在这项研究中,我们通过两种工程策略首次在酿酒酵母中设计了苯丙氨酸衍生的苄基芥子油苷的生产:稳定的基因组整合与基于质粒的生物合成基因导入。尽管质粒工程菌株在生物合成途径中的各基因(CYP83B1除外)表达水平普遍较高,基因组工程化菌株产生了更高的苄基芥子油苷生产水平。基于基因组工程菌株,优化提高了苄基硫葡萄糖苷水平。我们的研究比较了设计多基因途径以生产植物天然产物苄基芥子油苷的不同方法。这可以在工业生物技术中提供潜在的应用。
    Intake of brassicaceous vegetables such as cabbage is associated with numerous health benefits. The major defense compounds in the Brassicales order are the amino acid-derived glucosinolates that have been associated with the health-promoting effects. This has primed a desire to build glucosinolate-producing microbial cell factories as a stable and reliable source. Here, we established-for the first time-production of the phenylalanine-derived benzylglucosinolate (BGLS) in Saccharomyces cerevisiae using two different engineering strategies: stable genome integration versus plasmid-based introduction of the biosynthetic genes. Although the plasmid-engineered strain showed a tendency to generate higher expression level of each gene (except CYP83B1) in the biosynthetic pathway, the genome-engineered strain produced 8.4-fold higher BGLS yield compared to the plasmid-engineered strain. Additionally, we optimized the genome-engineered strain by overexpressing the entry point genes CYP79A2 and CYP83B1, resulting in a 2-fold increase in BGLS production but also a 4.8-fold increase in the level of the last intermediate desulfo-benzylglucosinolate (dsBGLS). We applied several approaches to alleviate the metabolic bottleneck in the step where dsBGLS is converted to BGLS by sulfotransferase, SOT16 dependent on 3\'-phosphoadenosine-5\'-phosphosulfate (PAPS). BGLS production increased 1.7-fold by overexpressing SOT16 and 1.7-fold by introducing APS kinase, APK1, from Arabidopsis thaliana involved in the PAPS regeneration cycle. Modulating the endogenous sulfur assimilatory pathway through overexpression of MET3 and MET14 resulted in 2.4-fold to 12.81 μmol/L (=5.2 mg/L) for BGLS production. IMPORTANCE Intake of brassicaceous vegetables such as cabbage is associated with numerous health benefits. The major defense compounds in the Brassicales order are the amino acid-derived glucosinolates that have been associated with the health-promoting effects. This has primed a desire to build glucosinolate-producing microbial cell factories as a stable and reliable source. In this study, we engineered for the first time the production of phenylalanine-derived benzylglucosinolate in Saccharomyces cerevisiae with two engineering strategies: stable genome integration versus plasmid-based introduction of the biosynthetic genes. Although the plasmid-engineered strain generally showed higher expression level of each gene (except CYP83B1) in the biosynthetic pathway, the genome-engineered strain produced higher production level of benzylglucosinolate. Based on the genome-engineered strain, the benzylglucosinolate level was improved by optimization. Our study compared different approaches to engineer a multigene pathway for production of the plant natural product benzylglucosinolate. This may provide potential application in industrial biotechnology.
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  • 文章类型: Journal Article
    在这项研究中,我们的目的是利用20个藻类菌株的可用基因组和转录组序列,探索病毒和绿枝树科绿藻(Chlorophyta)之间的水平基因转移。我们确定了大量与病毒同源物共享较高序列相似性的基因,因此发出信号,它们可能参与病毒的水平基因转移。进一步的表征表明,许多这些基因聚集在几十到几百千碱基大小的DNA区域,最初属于与已知的Tetraselmisspp有关的病毒。病毒(TetV和TsV)。相比之下,其余的候选HGT基因随机分散在藻类基因组中,更频繁地转录,属于大型多基因家族。病毒科中同源物的存在表明后者更可能是藻类而不是病毒来源。我们发现插入四叶蛇基因组中的波林顿样病毒(PLV)元件具有显着的多样性,所有这些都与四叶虫病毒(TsV)最相似。PLV元件的基因在转录上无活性,但功能未知的TsV的TVSG_00024基因的同源物明显例外。我们建议该基因可能参与前哨过程,以响应环境刺激而触发病毒的再激活和切除。总之,这些结果提供了证据表明TsV相关病毒具有双重生活方式,在游离病毒相(即病毒体)和整合到宿主基因组中的相之间交替。
    In this study, we aimed at exploring horizontal gene transfer between viruses and Chlorodendraceae green algae (Chlorophyta) using available genomic and transcriptomic sequences for twenty algal strains. We identified a significant number of genes sharing a higher sequence similarity with viral homologues, thus signalling their possible involvement in horizontal gene transfers with viruses. Further characterization showed that many of these genes were clustered in DNA regions of several tens to hundreds of kilobases in size, originally belonging to viruses related to known Tetraselmis spp. viruses (TetV and TsV). In contrast, the remaining candidate HGT genes were randomly dispersed in the algal genomes, were more frequently transcribed, and belonged to large multigene families. The presence of homologues in Viridiplantae suggested that the latter were more likely of algal rather than viral origin. We found a remarkable diversity in polinton-like virus (PLV) elements inserted in Tetraselmis genomes, all of which were most similar to the Tetraselmis striata virus (TsV). The genes of PLV elements are transcriptionally inactive with the notable exception of the homologue of the TVSG_00024 gene of TsV whose function is unknown. We suggest that this gene may be involved in a sentinel process to trigger virus reactivation and excision in response to an environmental stimulus. Altogether, these results provide evidence that TsV-related viruses have a dual lifestyle, alternating between a free viral phase (i.e. virion) and a phase integrated into host genomes.
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