engleski

Genomic composition and turnover of satellite DNA repeats

Eukaryotic genomes are to a large extent structured by repetitive sequences and remodeled by their evolution. Among them, satellite DNAs, non-coding DNA sequences repeated in tandem, are principal DNA components of heterochromatic chromosomal regions but can also appear as single units or as short arrays interspersed in euchromatic portions of the genome. Each genome can harbor many satellite DNAs, different in sequence and their origin, copy number and genomic distribution. Rapidly achieved dramatic interspecies differences in genomic content of satellite DNAs are, according to the library model, driven by expansions and contractions within a set of sequences common for a group of species. This phenomenon does not necessarily include dramatic alterations in satellite DNA sequences, which can remain well-conserved even during long evolutionary periods. Ability of satellite DNAs to persist in sequence and change rapidly in copy number may guarantee long-term stability of interactions involved in some basic functions of heterochromatic chromosomal segments, such as in and around centromeres, where rapid adjustments of DNA-protein interactions might be crucial for chromosomal integrity and function. The idea that mechanisms related to transposition may determine extensive satellite DNA array rearrangements is supported by sequence similarity shared between some transposable elements and satellite DNAs. For example, tandem repeats can be found as constitutive modules within a class of non-autonomous mobile element MITE (miniature inverted repeat transposable element), and related tandem repeats can appear in satellite DNA arrays. These features indicate that two distinct classes of repetitive sequences, satellite DNAs and mobile elements, are intertwined in a complex network of interrelated sequences and processes that eventually determine repetitive setup of the genome.

repetitive DNA; chromosome; centromere; evolution

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