Cell-cycle checkpoints are generally global in nature: one unattached kinetochore prevents the segregation of all chromosomes; stalled replication forks inhibit late origin firing throughout the genome. A potential exception to this rule is the regulation of replication fork progression by the S-phase DNA damage checkpoint. In this case, it is possible that the checkpoint is global, and it slows all replication forks in the genome. However, it is also possible that the checkpoint acts locally at sites of DNA damage, and only slows those forks that encounter DNA damage. Whether the checkpoint regulates forks globally or locally has important mechanistic implications for how replication forks deal with damaged DNA during S-phase.
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http://dx.doi.org/10.1042/BST20130197 | DOI Listing |
Int J Mol Sci
January 2025
Institute of Molecular Biology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl. 21, 1113 Sofia, Bulgaria.
Replication forks encounter various impediments, which induce fork stalling and threaten genome stability, yet the precise dynamics of fork stalling and restart at the single-cell level remain elusive. Herein, we devise a live-cell microscopy-based approach to follow hydroxyurea-induced fork stalling and subsequent restart at 30 s resolution. We measure two distinct processes during fork stalling.
View Article and Find Full Text PDFBiomolecules
January 2025
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
RAD18 is a conserved eukaryotic E3 ubiquitin ligase that promotes genome stability through multiple pathways. One of these is gap-filling DNA synthesis at active replication forks and in post-replicative DNA. RAD18 also regulates homologous recombination (HR) repair of DNA breaks; however, the current literature describing the contribution of RAD18 to HR in mammalian systems has not reached a consensus.
View Article and Find Full Text PDFCancer Chemother Pharmacol
January 2025
Cancer Therapeutics Program, UPMC Hillman Cancer Center, Pittsburgh, PA, USA.
Background: ATR is an apical DDR kinase activated at damaged replication forks. Elimusertib is an oral ATR inhibitor and potentiates irinotecan in human colorectal cancer models.
Methods: To establish dose and tolerability of elimusertib with FOLFIRI, a Bayesian Optimal Interval trial design was pursued.
The DNA damage response (DDR) mechanisms that allow cells to tolerate DNA replication stress are critically important for genome stability and cell viability. Using an unbiased genetic screen we identify a role for the RING finger E3 ubiquitin ligase RNF25 in promoting DNA replication stress tolerance. In response to DNA replication stress, RNF25-deficient cells generate aberrantly high levels of single-stranded DNA (ssDNA), accumulate in S-phase and show reduced mitotic entry.
View Article and Find Full Text PDFNat Chem Biol
January 2025
Department of Gynecology, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.
The regressed arms of reversed replication forks exhibit structural similarities to one-ended double-stranded breaks and need to be protected against uncontrolled nucleolytic degradation. Here, we identify MSANTD4 (Myb/SANT-like DNA-binding domain-containing protein 4), a functionally uncharacterized protein that uniquely counters the replication protein A (RPA)-Bloom (BLM)/Werner syndrome helicase (WRN)-DNA replication helicase/nuclease 2 (DNA2) complex to safeguard reversed replication forks from detrimental degradation, independently of the breast cancer susceptibility proteins (BRCA1/2)-DNA repair protein RAD51 pathway. MSANTD4 specifically interacts with the junctions between single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) in DNA substrates harboring a 3' overhang, which resemble the structural features of regressed arms processed by WRN-DNA2.
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