engleski

Some future aspects of research: heterochromatic DNA, siRNAs and chromatin silencing

Heterochromatic DNA, composed mostly of tandemly repeated sequences or satellite DNAs, encompasses the pericentromeres as well as regions of centromere in most eukaryotes. It differs significantly in sequence and composition even between closely related species. Recent results suggest that satellite DNA evolution is driven by stochastic process and by selective pressure and proceeds in a manner that retains some architectural features or structural domains. It is probably followed by adaptive evolution of the corresponding DNA binding proteins like specific centromeric histones. In addition to the performing a structural role, heterochromatic DNA is transcribed in a developmentally regulated manner. Processed transcripts in the form of small interfering RNAs (siRNAs), 20-24 nt long, trigger the formation of silent chromatin (heterochromatin). This is probably achieved by recruitment of chromatin-modifying enzymes that promote histone methylation necessary for the heterochromatin formation and centromere function. In this way, heterochromatic DNA, through siRNA transcripts, acts as an epigenetic signal for the establishment of chromatin organization required for chromosome segregation. Further studies are needed in order to get a deeper understanding of the biological role of heterochromatic DNA and siRNAs.

heterochromatin; siRNA; satellite DNA; chromatin-modifying enzymes

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