Replisome loading reduces chromatin motion independent of DNA synthesis
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Date
2023-07-07
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Chromatin has been shown to undergo diffusional motion, and during active gene transcription the RNA
polymerase activity negatively affects chromatin motion. However, the relationship between chromatin motion
and other genomic processes remains unclear. Hence, we set out to label the DNA directly in a sequence
unbiased manner and recorded labeled chromatin dynamics in interphase human cells expressing GFP-tagged
PCNA, a cell cycle marker and core component of the replication machinery. We detected decreased
chromatin mobility during S-phase compared to G1 and G2 phases using automated particle tracking. To gain
insight into the organization and dynamics of the genome during DNA replication, we analyzed labeled
chromatin domain size and motion in replicating cells. By correlating chromatin mobility with proximity to sites
of active DNA synthesis, we show that chromatin motion is locally constrained at the sites of DNA replication.
Furthermore, inhibiting DNA synthesis activity leads to increase loading of DNA polymerases and further
restricts local chromatin motion. The polymerases under stress no longer reel DNA through, as they normally
do during DNA synthesis, which may explain the further restriction of chromatin motion and the fact that
loading the helicase/polymerase already restricts it during active DNA synthesis. We, therefore, propose that
increased polymerase loading but not their catalytic activity reduces genome dynamics and its accessibility
and interaction with other genomic regions.
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Except where otherwise noted, this license is described as CC-BY-NC 4.0 - Attribution-NonCommercial 4.0 International