Perspective Article: Space-time dynamics of genome replication studied with super-resolved microscopy
Bibliographic record
Abstract
Genome replication requires duplication of the complete set of DNA sequences together with nucleosomes and epigenetic signatures. Notwithstanding profound knowledge on mechanistic details of DNA replication, major problems of genome replication have remained unresolved. In this perspective article, we consider the accessibility of replication machines to all DNA sequences in due course, the maintenance of functionally important positional and structural features of chromatid domains during replication, and the rapid transition of CTs into prophase chromosomes with two chromatids. We illustrate this problem with EdU pulse-labeling (10 min) and chase experiments (80 min) performed with mouse myeloblast cells. Following light optical serial sectioning of nuclei with 3D structured illumination microscopy (SIM), seven DNA intensity classes were distinguished as proxies for increasing DNA compaction. In nuclei of cells fixed immediately after the pulse-label, we observed a relative under-representation of EdU-labeled DNA in low DNA density classes, representing the active nuclear compartment (ANC), and an over-representation in high density classes representing the inactive nuclear compartment (INC). Cells fixed after the chase revealed an even more pronounced shift to high DNA intensity classes. This finding contrasts with previous studies of the transcriptional topography demonstrating an under-representation of epigenetic signatures for active chromatin and RNAPII in high DNA intensity classes and their over-representation in low density classes. We discuss these findings in the light of current models viewing CDs either as structural chromatin frameworks or as phase-separated droplets, as well as methodological limitations that currently prevent an integration of this contrasting evidence for the spatial nuclear topography of replication and transcription into a common framework of the dynamic nuclear architecture.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".