A tale of two marks: dual modifications on an histone H3.3 govern gene silencing and X-chromosome inactivation
Peer-Reviewed Publication
Updates every hour. Last Updated: 18-Jun-2026 08:16 ET (18-Jun-2026 12:16 GMT/UTC)
Scientists have deciphered a long-standing paradox of the histone variant H3.3: how the same protein can mark both active and silenced regions of the genome. The key lies in a specific combination of modifications—phosphorylation at serine 31 (Ser31p) together with trimethylation at lysine 27 (K27me3). This dual “code” on H3.3 acts as a master switch, recruiting protein complexes that establish H3K9me3-marked heterochromatin, a repressive chromatin state. The study demonstrates that this “H3.3–CBX7–KAP1–H3K9me3” pathway is essential for silencing repetitive DNA elements and, crucially, for the epigenetic silencing of one X chromosome in females, a process vital for mammalian development.
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The protein “neurofilament light chain” (NfL) – studied in humans in the context of neurodegenerative diseases and aging – is also detectable in the blood of numerous animals, and NfL levels increase with age in mice, cats, dogs, and horses. Experts from the DZNE and the Hertie Institute for Clinical Brain Research (HIH) at the University of Tübingen report these findings in the scientific journal “PLOS Biology”. In their view, this biomarker could help to assess the biological age of animals and estimate their life expectancy.
A study led by the Institute for Bioengineering of Catalonia (IBEC) and the Molecular Biology Institute of Barcelona (IBMB) provides the most detailed picture to date of NrdR — the master regulator of ribonucleotide reductases (RNRs) in bacteria. Researchers obtained the first detailed images of the complete NrdR protein structure and showed how changes in the shape and grouping of this protein affect the way it controls key processes inside the cell. The findings, recently published in International Journal of Biological Macromolecules, increase our understanding of how bacteria regulate the production of the molecular building blocks of DNA, a crucial aspect for both fundamental microbiology and the development of new antimicrobial strategies.
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