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Researchers discovered that DNA sequences derived from Helitron transposons in C. elegans can act as physical barriers to separate active and silent chromatin regions, independent of insulator proteins. These sequences have evolved a 10-base-pair periodic pattern that creates intrinsic DNA curvature, which disrupts normal nucleosome formation and prevents the spread of gene-silencing chromatin marks. Similar mechanical DNA signatures appear across diverse animal species, suggesting this represents a widespread, sequence-based mechanism for genome organization that evolved from selfish genetic elements.
Why it matters
This finding reveals a previously unrecognized physical mechanism for protecting gene expression that does not require specific protein binding sites. Understanding how DNA sequence itself can create functional boundaries may inform therapeutic approaches for diseases involving abnormal gene silencing and provide new strategies for genome engineering.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Genomes require physical boundaries to separate active and repressed chromatin, a function traditionally attributed to insulator proteins. Here, we show that genomic insulation can also emerge from physical properties encoded directly within the DNA polymer. In C. elegans, transcription-coupled mutational bias remodels Helitron transposon minisatellites to match the DNA helical repeat. The resulting 10-bp periodicity (PATCs) encodes intrinsic curvature, creating topologically responsive DNA elements that favor local deformation under supercoiling, disrupt canonical nucleosome organization, and protect germline genes from progressive and heritable silencing. Rather than acting as short protein-binding motifs, Helitron-derived PATCs form extended barrier elements that limit the stabilization of repressive chromatin. Comparative analyses suggest that related sequence-encoded mechanical signatures recur across Metazoa, including at Drosophila insulators, human CTCF sites, and active human LINE-1 retrotransposons. Thus, sequence-encoded mechanics provide an evolutionarily accessible substrate for chromatin insulation–a physical layer of genome organization that can be co-opted by host genomes to protect gene expression, and potentially retained by selfish elements for their own persistence.
Source: Evolution of mechanical chromatin insulators from selfish genetic elements