Transposable elements (TEs), once considered genomic "junk", are now recognized as critical regulators of genome function and human disease. These mobile genetic elements-including retrotransposons (long interspersed nuclear elements [LINE-1], Alu, short interspersed nuclear element-variable numbers of tandem repeats-Alu [SVA], and human endogenous retrovirus [HERV]) and DNA transposons-are tightly regulated by multilayered mechanisms that operate from transcription through to genomic integration. Although typically silenced in somatic cells, TEs are transiently activated during key developmental stages-such as zygotic genome activation and cell fate determination-where they influence chromatin architecture, transcriptional networks, RNA processing, and innate immune responses. Dysregulation of TEs, however, can lead to genomic instability, chronic inflammation, and various pathologies, including cancer, neurodegeneration, and aging. Paradoxically, their reactivation also presents new opportunities for clinical applications, particularly as diagnostic biomarkers and therapeutic targets. Understanding the dual role of TEs-and balancing their contributions to normal development and disease-is essential for advancing novel therapies and precision medicine.
Humans ; DNA Transposable Elements/physiology* ; Animals ; Long Interspersed Nucleotide Elements/genetics* ; Neoplasms/genetics* ; Genomic Instability/genetics* ; Endogenous Retroviruses/genetics*

Mammalian fertilization begins with the fusion of two specialized gametes, followed by major epigenetic remodeling leading to the formation of a totipotent embryo. During the development of the pre-implantation embryo, precise reprogramming progress is a prerequisite for avoiding developmental defects or embryonic lethality, but the underlying molecular mechanisms remain elusive. For the past few years, unprecedented breakthroughs have been made in mapping the regulatory network of dynamic epigenomes during mammalian early embryo development, taking advantage of multiple advances and innovations in low-input genome-wide chromatin analysis technologies. The aim of this review is to highlight the most recent progress in understanding the mechanisms of epigenetic remodeling during early embryogenesis in mammals, including DNA methylation, histone modifications, chromatin accessibility and 3D chromatin organization.
Animals ; Chromatin Assembly and Disassembly ; DNA Methylation ; DNA Transposable Elements ; Embryo, Mammalian ; Embryonic Development/genetics* ; Epigenesis, Genetic ; Epigenome ; Female ; Fertilization/physiology* ; Gene Expression Regulation, Developmental ; Histone Code ; Histones/metabolism* ; Male ; Mice ; Oocytes/metabolism* ; Spermatozoa/metabolism*

AIMTo elucidate the genetic basis for the pronounced resistance that the oral pathogen, Porphyromonas gingivalis (P. gingivalis), exhibits towards the cationic antimicrobial peptide, polymyxin B.

METHODOLOGYA genetic screen of P. gingivalis clones generated by a Tn4400'-based random insertion mutagenesis strategy was performed to identify bacteria harboring novel genetic mutations that render P. gingivalis susceptible to killing by the cationic antimicrobial peptide, polymyxin B (PMB, 50 microg x mL(-1)).

RESULTSP. gingivalis (ATCC 33277) is unusually resistant to the cationic antimicrobial peptide, PMB at relatively high concentrations (200 microg x mL(-1)). Approximately 2,700 independent Tn4400'-derived mutants of P. gingivalis were examined for increased sensitivity to PMB killing at a relatively low dose (50 microg x mL(-1)). A single PMB-sensitive mutant was obtained in this phenotypic screen. We determined that the Tn4400' transposon was integrated into the gene encoding the lipid A 4'-phosphatase, PGN_0524, demonstrating that this insertion event was responsible for its increased susceptibility of this clone to PMB-dependent killing. The resulting mutant strain, designated 0524-Tn4400', was highly sensitive to PMB killing relative to wild-type P. gingivalis, and exhibited the same sensitivity as the previously characterized strain, 0524KO, which bears a genetically engineered deletion in the PGN_0524 locus. Positive ion mass spectrometric structural (MALDI-TOF MS) analyses revealed that lipid A isolates from 0524-Tn4400' and 0524KO strains displayed strikingly similar MALDI-TOF MS spectra that were substantially different from the wildtype P. gingivalis lipid A spectrum. Finally, intact 0524-Tn4400' and 0524KO mutant bacteria, as well as their corresponding LPS isolates, were significantly more potent in stimulating Toll-like receptor 4 (TLR4)-dependent E-selectin expression in human endothelial cells relative to intact wild-type P. gingivalis or its corresponding LPS isolate.

CONCLUSIONThe combined molecular evidence provided in this report suggests that PGN_0524, a lipid A 4'-phosphatase, is the sole genetic element conferring the ability of the periodontopathogen, P. gingivalis, to evade the killing activity of cationic antimicrobial peptides, such as PMB. These data strongly implicate PGN_0524 as a critical virulence factor for the ability of P. gingivalis to evade front-line host innate defenses that are dependent upon cationic antimicrobial peptide activity and TLR 4 sensing.

Anti-Bacterial Agents ; pharmacology ; Chromosome Mapping ; DNA Transposable Elements ; genetics ; Drug Resistance, Bacterial ; genetics ; E-Selectin ; analysis ; immunology ; Endothelial Cells ; immunology ; microbiology ; Gene Deletion ; Humans ; Lipid A ; analysis ; immunology ; Lipopolysaccharides ; analysis ; immunology ; Mutagenesis, Insertional ; genetics ; Open Reading Frames ; genetics ; Phosphoric Monoester Hydrolases ; genetics ; physiology ; Polymyxin B ; pharmacology ; Porphyromonas gingivalis ; enzymology ; genetics ; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ; Toll-Like Receptor 4 ; analysis ; immunology ; Virulence Factors ; physiology

The mutant population of Xanthomonas oryzae pv oryzae strain differential to rice bacterial blight resistance gene Xa23 has been constructed mediated by transposon in vivo . The results of PCR amplification with specific primers and analysis of flanking sequence of mutants indicated that the foreign DNA has been integrated into X. oryzae pv oryzae genome. Four mutants with changed avirulent activity to Xa23 gene have been identified by artificial inoculation. It is possible to clone genes that are required for AvrXa23 avirulence activity using this new strategy.
Bacterial Proteins ; genetics ; Base Sequence ; DNA Transposable Elements ; Gene Expression Regulation, Plant ; Genes, Plant ; Molecular Sequence Data ; Mutation ; Oryza ; genetics ; microbiology ; Plant Diseases ; microbiology ; Plants, Genetically Modified ; genetics ; microbiology ; Virulence ; Xanthomonas ; genetics ; pathogenicity ; physiology

Chromosomal virulence genes acvB, abvA, chvA of Agrobacterium tumefaciens were cloned with the technique of transposon 5 insertion. The chromosome genes are necessary for Agrobacterium tumfaciens absorbing to cell ular surface of plant, the adherence reaction can't be executed and result in losing the toxicity if mutations are occurred in some chromosome genes. The chromosome toxicity gene is inactivated due to transposon Tn5 be inserted and the accept ant cell infected with Agrobacterium tumefaciens can't cause tumor ultimately. This article briefly introduces the research way of thinking and strategy of this technique and the important roles of every gene, which are taken of in the process of T-DNA's form, transfer, integration, and expression etc. This article also gives a presumption to T-DNA's transport: The plant cell wall's porin may be T-DNA's natural channel.
Agrobacterium tumefaciens ; genetics ; metabolism ; pathogenicity ; DNA Transposable Elements ; genetics ; physiology ; Virulence ; genetics

Present studies describe the successful establishment of Spodoptera exigua multicapsid nucleopolyhedrovirus (SeMNPV) BAC-TO-BAC expression system. The mini-F-lacZ-attTn7-kan fragment (Luckow et al, 1993) was inserted into SeMNPV US1 isolate (SeUS1) at polyhedrin gene locus by directly cloning. The recombinant virus containing low-copy-number mini-F replication, which named bacmid, can propagate in Escherichia coli. Because SeUS1 isolate is make up of several genotypes and one bacmid carries one SeMNPV genotype, the SeUS1 BAC library is established by all SeMNPV bacmids (SeBAC). REN analysis for 111 SeBAC shows that SeUS1 consists of the genotype with whole SeMNPV genetic information and several genotypes with various different deletions. Progeny virus can be produced in insect cell line after transfection with SeBAC10, which carries the whole SeMNPV genome. So SeBAC10 is a shuttle vector that can replicate in eukaryocyte as well as prokaryocyte. Considering the insert mutation of SeMNPV polyhedrin gene (Seph) in SeBAC10, Seph was reintroduced into the bacmid by site-specific transposon-mediated insertion at attTn7, the target site for the bacterial transposon Tn7. The derived recombinant SeBAC10 was named SeBAC10ph. After SeBAC10ph was transfected into Se301 cells (a susceptible insect cell line to SeMNPV), cytopathogenic effect was shown and polyhedra appeared, which indicate that the foreign gene (Seph) is expressed.
Animals ; Cell Line ; Chromosomes, Artificial, Bacterial ; genetics ; DNA Transposable Elements ; genetics ; Genetic Vectors ; genetics ; Models, Theoretical ; Nucleopolyhedrovirus ; genetics ; physiology ; Spodoptera ; cytology ; virology ; Viral Structural Proteins ; genetics