van Batenburg, V. | bioRxiv Science

bioRxiv2024

Acute multi-level response to defective de novo chromatin assembly in S-phase

Long-term perturbation of de novo chromatin assembly during DNA replication has profound effects on epigenome maintenance and cell fate. The early mechanistic origin of these defects is unknown. Here, we combine acute degradation of Chromatin Assembly Factor 1 (CAF-1), a key player in de novo chromatin assembly, with single-cell genomics, quantitative proteomics, and live-microscopy to uncover these initiating mechanisms in human cells. CAF-1 loss immediately slows down DNA replication speed and renders nascent DNA hyper-accessible. A rapid cellular response, distinct from canonical DNA damage signaling, is triggered and lowers histone mRNAs. As a result, histone variants usage and their modifications are altered, limiting transcriptional fidelity and delaying chromatin maturation within a single S-phase. This multi-level response induces a cell-cycle arrest after mitosis. Our work reveals the immediate consequences of defective de novo chromatin assembly during DNA replication, explaining how at later times the epigenome and cell fate can be altered. HighlightsO_LIThe histone chaperone CAF-1 sustains DNA replication speed in single cells. C_LIO_LICAF-1 loss alters histone repertoire and delays chromatin maturation. C_LIO_LIH3K9me3 and H3K27me3 regions respond differently to acute CAF-1 depletion. C_LIO_LIImpaired S-phase chromatin assembly triggers an immediate response and a G0 arrest. C_LI

cell biology↗

bioRxiv2022

Acceleration of genome replication uncovered by single-cell nascent DNA sequencing

In a human cell thousands of replication forks simultaneously coordinate the duplication of the entire genome. The rate at which this process occurs, might depend on the epigenetic state of the genome and vary between, or even within, cell types. To accurately measure DNA replication speeds, we developed a technology to detect recently replicated DNA using single-cell sequencing. Replication speed is not constant but increases during S-phase of the cell cycle. Using genetic and pharmacological perturbations we are able to alter this acceleration of replication and conclude that DNA damage inflicted by the process of transcription limits the speed of replication during early S-phase. In late S-phase, during which less transcription occurs, replication accelerates and approaches its maximum speed.

molecular biology↗