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Although DNA N 6-adenine methylation (6mA) is best known in prokaryotes, its presence in eukaryotes has recently generated great interest. Biochemical and genetic evidence supports that AMT1, an MT-A70 family methyltransferase (MTase), is crucial for 6mA deposition in unicellular eukaryotes. Nonetheless, the 6mA transmission mechanism remains to be elucidated. Taking advantage of single-molecule real-time circular consensus sequencing (SMRT CCS), here we provide definitive evidence for semiconservative transmission of 6mA in Tetrahymena thermophila In wild-type (WT) cells, 6mA occurs at the self-complementary ApT dinucleotide, mostly in full methylation (full-6mApT); after DNA replication, hemi-methylation (hemi-6mApT) is transiently present on the parental strand, opposite to the daughter strand readily labeled by 5-bromo-2-deoxyuridine (BrdU). In ΔAMT1 cells, 6mA predominantly occurs as hemi-6mApT. Hemi-to-full conversion in WT cells is fast, robust, and processive, whereas de novo methylation in ΔAMT1 cells is slow and sporadic. In Tetrahymena, regularly spaced 6mA clusters coincide with the linker DNA of nucleosomes arrayed in the gene body. Importantly, in vitro methylation of human chromatin by the reconstituted AMT1 complex recapitulates preferential targeting of hemi-6mApT sites in linker DNA, supporting AMT1s intrinsic and autonomous role in maintenance methylation. We conclude that 6mA is transmitted by a semiconservative mechanism: full-6mApT is split by DNA replication into hemi-6mApT, which is restored to full-6mApT by AMT1-dependent maintenance methylation. Our study dissects AMT1-dependent maintenance methylation and AMT1-independent de novo methylation, reveals a 6mA transmission pathway with a striking similarity to 5-methylcytosine (5mC) transmission at the CpG dinucleotide, and establishes 6mA as a bona fide eukaryotic epigenetic mark.

Microorganisms have expanded our understanding of biodiversity and exhibit crucial research values. Ciliated protists are a highly differentiated group of eukaryotic microorganisms with exceptional features, such as numerous cilia, dimorphic nuclei, and genome-wide gene rearrangement, that have made them ideal research models for revealing many biological processes. Studies of the ciliate Tetrahymena thermophila have greatly advanced our understanding of RNA self-splicing and enzymatic activity, telomere biology, and the Nobel Prize-winning telomerase mechanisms. Genome rearrangement during the sexual reproduction (conjugation) of ciliates, involving the elimination of ~25–90% of germline DNA, provides an opportunity to study large-scale genome remodelling while also revealing a more thorough mode of transposon repression, i.e. Piwi-interacting small RNA-mediated DNA deletion in the somatic nucleus. Although much progress has been made, research has focused mainly on a few model species that are amenable to gene editing. For other species, although they are more suitable to address some scientific gaps, research cannot be carried out owing to limitations of genetic engineering. Here, we summarize the existing genetic engineering strategies for ciliates, expecting to provide inspiration for the development and optimization of genetic engineering tools for ciliates and other organisms cannot yet be edited genetically. [ABSTRACT FROM AUTHOR]

Ciliates usually with big cell sizes, complex morphological structures, and diverse life cycles, are good model organisms for studying cell proliferation regulation of eukaryotes. Up to date, the molecular regulation mechanisms for the vegetative cell cycle and encystment of these ciliates are poorly understood. Here, transcriptomes of Apodileptus cf. visscheri, which has an asexual vegetative cell cycle and is apt to encyst when environmental conditions become unfavorable, were sequenced to enrich our related knowledge. In this study, three replicates were sequenced for each of four cell stages, including initial period of growth, morphogenesis, cell division, and resting cyst. The significant transcription differences, involving cell cycle, biosynthesis, and energy metabolism pathways, were revealed between the resting cyst and vegetative cell cycle. Further investigations showed that the cell cycle pathway was enriched during morphogenesis stage and cell division stage. Compared to the initial period of growth stage, the differentially expressed genes involved in cellular components and molecular function were significantly enriched during cell division stage, while cellular components and biological processes were significantly enriched during morphogenesis stage. These provide novel insights into a comprehensive understanding at the molecular level of the survival and adaptive mechanism of unicellular eukaryotes. [ABSTRACT FROM AUTHOR]

The new energy industry has increasingly higher requirements for the lightweight design and functional integration of the power energy system. As an effective solution to achieve this demand, a structural energy storage integrated composite was prepared that consists of a functional body with an ideal specific capacity combined with considerable mechanical properties. In this study, we prepared a CF@Mn3O4 composite by compounding polyacrylonitrile (PAN)-based carbon fiber (CF) with Mn3O4 through the three-step method of acid leaching activation, hydrothermal stirring, and high temperature annealing. As a result, the CF@Mn3O4 composite maintains a specific capacity of 610.5 mA h g−1 after 150 cycles at the current density of 100 mA g−1, which is approximately 2.48 times higher than that of the carbon fiber. The tensile strength, Young's modulus, and elongation of the CF@Mn3O4 composite reached 92.1%, 94.5%, and 93.5% of the original carbon fiber. These significant mechanical and electrochemical characteristics can be attributed to the synergistic effect of the carbon fiber substrate and Mn3O4. The carbon fiber served as a buffer substrate to relieve the volume expansion of the deposited layer during the charging and discharging processes, and the Mn3O4 was used as a coating layer to provide more insertion sites for lithium ions, which enables a higher charge–discharge specific capacity. [ABSTRACT FROM AUTHOR]

Metallic antimony is considered to be a promising anode material for lithium ion batteries (LIBs) due to its appropriate reaction potential. However, the rapid loss of capacity during the cycling process restricts its practical application. Hence, it is essential to research for a facile and effective approach for a new high-capacity antimony trioxide as an anode material for LIBs. In this study, we successfully synthesized an Sb2O3/Sb@TiO2 composite, wherein the TiO2 film was coated on the surface of Sb2O3 nanorods with the discontinuous distribution of elemental Sb particles in the TiO2 film. The Sb2O3/Sb@TiO2 composite exhibits superior rate and cycling performance. As an anode material, a specific discharge capacity of 609 mA h g−1 can be released at a current density of 100 mA g−1. The excellent electrochemical performance is based on Sb nanoparticles and one-dimensional Sb2O3 as the core to enhance the capacity, and TiO2 is used as the outer shell to consolidate the interface between the electrolyte and the electrode material. [ABSTRACT FROM AUTHOR]

N 6 -methyladenine DNA (6mA) modification exists in both prokaryotes and eukaryotes in which it plays a crucial role in regulating numerous biological processes. In prokaryotes, 6mA is a marker to distinguish self from foreign DNA. Its role in eukaryotes, however, remains elusive. Ciliates were among the first eukaryotes reported to contain 6mA. In the model organism T. thermophila , cellular localization and features of 6mA have been extensively studied, especially in ribosomal DNA (rDNA) molecules. Here, we summarize the features and potential functions of 6mA in Tetrahymena thermophila and other ciliates, and the major findings and contributions of the Tetrahymena model in studies of 6mA methylation. We also discuss other questions in order to improve understanding of the function and evolution of 6mA in eukaryotes. [ABSTRACT FROM AUTHOR]

Although DNA N 6 -adenine methylation (6mA) is best known in prokaryotes, its presence in eukaryotes has recently generated great interest. Biochemical and genetic evidence supports that AMT1, an MT-A70 family methyltransferase (MTase), is crucial for 6mA deposition in unicellular eukaryotes. Nonetheless, the 6mA transmission mechanism remains to be elucidated. Taking advantage of single-molecule real-time circular consensus sequencing (SMRT CCS), here we provide definitive evidence for semiconservative transmission of 6mA in Tetrahymena thermophila In wild-type (WT) cells, 6mA occurs at the self-complementary ApT dinucleotide, mostly in full methylation (full-6mApT); after DNA replication, hemi-methylation (hemi-6mApT) is transiently present on the parental strand, opposite to the daughter strand readily labeled by 5-bromo-2'-deoxyuridine (BrdU). In Δ AMT1 cells, 6mA predominantly occurs as hemi-6mApT. Hemi-to-full conversion in WT cells is fast, robust, and processive, whereas de novo methylation in Δ AMT1 cells is slow and sporadic. In Tetrahymena , regularly spaced 6mA clusters coincide with the linker DNA of nucleosomes arrayed in the gene body. Importantly, in vitro methylation of human chromatin by the reconstituted AMT1 complex recapitulates preferential targeting of hemi-6mApT sites in linker DNA, supporting AMT1's intrinsic and autonomous role in maintenance methylation. We conclude that 6mA is transmitted by a semiconservative mechanism: full-6mApT is split by DNA replication into hemi-6mApT, which is restored to full-6mApT by AMT1-dependent maintenance methylation. Our study dissects AMT1-dependent maintenance methylation and AMT1-independent de novo methylation, reveals a 6mA transmission pathway with a striking similarity to 5-methylcytosine (5mC) transmission at the CpG dinucleotide, and establishes 6mA as a bona fide eukaryotic epigenetic mark., (© 2024 Sheng et al.; Published by Cold Spring Harbor Laboratory Press.)