DNA knots occur in intracellular chromatin.
Nucleic Acids Res
; 46(2): 650-660, 2018 01 25.
Article
em En
| MEDLINE
| ID: mdl-29149297
ABSTRACT
In vivo DNA molecules are narrowly folded within chromatin fibers and self-interacting chromatin domains. Therefore, intra-molecular DNA entanglements (knots) might occur via DNA strand passage activity of topoisomerase II. Here, we assessed the presence of such DNA knots in a variety of yeast circular minichromosomes. We found that small steady state fractions of DNA knots are common in intracellular chromatin. These knots occur irrespective of DNA replication and cell proliferation, though their abundance is reduced during DNA transcription. We found also that in vivo DNA knotting probability does not scale proportionately with chromatin length it reaches a value of â¼0.025 in domains of â¼20 nucleosomes but tends to level off in longer chromatin fibers. These figures suggest that, while high flexibility of nucleosomal fibers and clustering of nearby nucleosomes facilitate DNA knotting locally, some mechanism minimizes the scaling of DNA knot formation throughout intracellular chromatin. We postulate that regulation of topoisomerase II activity and the fractal architecture of chromatin might be crucial to prevent a potentially massive and harmful self-entanglement of DNA molecules in vivo.
Texto completo:
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Base de dados:
MEDLINE
Assunto principal:
DNA Fúngico
/
DNA Super-Helicoidal
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Cromatina
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Conformação de Ácido Nucleico
Idioma:
En
Revista:
Nucleic Acids Res
Ano de publicação:
2018
Tipo de documento:
Article