This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Human genomic DNA is wrapped around core histone proteins to form nucleosomes, the fundamental units of chromatin. During interphase, the period between cell divisions, DNA is replicated and the nucleus becomes larger.
At the same time, cells must continuously carry out essential genome functions such as transcription, DNA replication and DNA repair. How the behavior of genomic DNA is maintained during these large changes has remained unclear. A research team led by professor Kazuhiro Maeshima at the National Institute of Genetics (NIG) and SOKENDAI, Japan, has now shown that average local DNA motion remains nearly constant throughout interphase in living human cells.
The researchers also found that this motion is not just constant: it can increase in response to cellular perturbations such as transcription inhibition, replication stress and DNA damage. In a previous study, the team showed using synchronized human cells that local chromatin motion remained nearly constant throughout G1, S and G2 phases. The present study tested whether this behavior is also observed in asynchronously growing cells without drug-induced synchronization.
The paper is published in the Journal of Cell Science. To study DNA motion during the cell cycle under physiological conditions, the researchers combined single-nucleosome imaging with fluorescent cell-cycle indicators known as Fucci probes. Fucci probes change their fluorescent color according to cell-cycle progression, allowing the researchers to identify the cell-cycle stage of individual living cells without using prolonged drug treatments to synchronize them.
By labeling the core histone H2B with HaloTag, which can mark bulk DNA, the researchers were able to visualize and track individual nucleosomes in living human cells. They then combined these measurements with Fucci signals to determine how local nucleosome motion changes as cells progress from G1 through S to G2 phase. Using asynchronously growing cells, the team found that average local nucleosome motion remained nearly constant throughout interphase.
This means average local DNA motion remained nearly constant throughout interphase. This stability is notable because major physical changes occur during the same period. As genomic DNA doubles, nuclear volume increases substantially.
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