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N4-methylcytosine (4mC) is an important DNA modification in prokaryotes, but its relevance and even its presence in eukaryotes have been mysterious. Here we show that spermatogenesis in the liverwort Marchantia polymorpha involves two waves of extensive DNA methylation reprogramming. First, 5-methylcytosine (5mC) expands from transposons to the entire genome. Notably, the second wave installs 4mC throughout genic regions, covering over 50% of CG sites in sperm. 4mC requires a methyltransferase (MpDN4MT1a) that is specifically expressed during late spermiogenesis. Deletion of MpDN4MT1a alters the sperm transcriptome, causes sperm swimming and fertility defects, and impairs post-fertilization development. Our results reveal extensive 4mC in a eukaryote, identify a family of eukaryotic methyltransferases, and elucidate the biological functions of 4mC in reproductive development, thereby expanding the repertoire of functional eukaryotic DNA modifications.
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http://dx.doi.org/10.1016/j.cell.2025.03.014 | DOI Listing |
ISME J
August 2025
School of Oceanography & Astrobiology Program, University of Washington, Seattle, WA, USA.
Despite growing evidence for the role of DNA methylation in bacterial acclimation to environmental stress, this epigenetic mechanism remains unexplored in sea-ice microbial communities known to tolerate multiple stressors. This study presents a first analysis of DNA methylation patterns in bacterial communities and associated viruses across the vertical thickness of sea ice. Using a novel stepped-sackhole method, we collected sea-ice brines from distinct horizons of an Arctic ice floe, capturing microbial communities that had been exposed to different environmental conditions.
View Article and Find Full Text PDFBMC Microbiol
August 2025
Institute of Med. Microbiology and Hospital Hygiene, Heinrich-Heine-University Duesseldorf, Duesseldorf, Germany.
Restriction-modification (RM) systems are widespread defense mechanisms in prokaryotes that protect the host from potentially harmful foreign DNA. They typically consist of a DNA methyltransferase (MTase), which methylates the host genome at an adenine (6 mA methylation) or cytosine (4mC or 5mC), and a restriction endonuclease (REase), which cleaves foreign, unmethylated DNA. In addition to the 2023 published family of 5mC-MTases, an HgaI-homolog RM system was detected in Mycoplasma hominis with the more rare constellation of two 5mC MTase genes, called RM.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
August 2025
Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, P.R. China.
Two paramagnetic Cr(I) complexes with homoleptic fac-bis(triarylisocyanide) ligands were prepared by chemical oxidation of the Cr(0) precursors and emission spectra with peak maximum at respective 568 and 525 nm have been recorded with THF solutions of these two low-spin d metal complexes at 298 K. Structural, spectroscopic, and theoretical studies revealed that the emission of the Cr(I) complexes could be tentatively assigned to be spin-allowed MLCT excited states. Femtosecond-resolved transient absorption spectra confirmed that the lifetimes of the excited states were in the tens of picoseconds, which could be explained by the fast nonradiative decay of MLCT state through low-lying quartet metal-centered (MC) states.
View Article and Find Full Text PDFZhongguo Xiu Fu Chong Jian Wai Ke Za Zhi
August 2025
Department of Orthopaedics, Shandong Provincial Qianfoshan Hospital, the First Affiliated Hospital of Shandong First Medical University, Jinan Shandong, 250012, P. R. China.
Objective: To investigate the effects of 4-methylcatechol (4MC) on the migration and inflammatory response in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS), as well as its underlying mechanisms of action.
Methods: RA-FLS was isolated from synovial tissue donated by RA patients, and the optimal concentration of 4MC was determined by cell counting kit 8 method for subsequent experiments, and the effect of 4MC on the migratory ability of RA-FLS was evaluated via a cell scratch assay. An inflammation model of RA-FLS was induced by tumor necrosis factor α (TNF-α).
Chemistry
August 2025
Centre for Analysis and Synthesis, Department of Chemistry, Lund University, Box 124, SE-22100, Lund, Sweden.
Fe complexes based on the [Fe(ImP)] motif (ImP = bis(2,6-bis(3-methylimidazol-2-ylidene-1-yl)phenylene)), where the ligand contains both carbene and cyclometalated moieties, are a promising class of photoactive materials made from this abundant metal. In this work, it is shown that bromo or furanyl substituents attached to the cyclometalating moiety of the ImP ligands stabilize the LMCT excited state to very different extent resulting in opposing effects on the LMCT lifetime. For [Fe(ImPBr)], the lifetime (255 ps) of its moderately stabilized LMCT state (1.
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