Biology subjects

Baldacci, G.

Publications and source records attributed to Baldacci, G..

3 recordsLinked to original sources

bioRxiv2025

PARP inhibitors affect the replisome and replication fork progression during a single S phase.

Poly(ADP-ribosyl)ation (PARylation) is a protein modification mostly synthesised and degraded by PARP1/2 and PARG enzymes, respectively. PARylation is involved in many covalent and non-covalent protein-protein interactions in the nucleus, making it a powerful form of molecular signaling in DNA metabolism. PARP inhibitors (PARPi) have shown efficacy in the treatment of Homologous Recombination (HR)-deficient cancers, yet the full range of molecular mechanisms underlying the activity of these drugs is not fully understood. Here, we decipher the direct consequences of PARPi-induced loss of PARylation on DNA replication. First, PARPi treatment during a single S phase induces replicative stress, delays S phase progression and causes genome-wide replication timing changes of disease-associated regions. These DNA replication alterations appear to be caused by an accumulation of SSBs in the DNA replicative template when PARylation is inhibited, which then seems to lead to one-ended DSBs and fork collapse during S phase. Second, PARPi deplete FANCD2-I, BRCA, monoubiquitinated PCNA and RAD18 proteins from the replisomes. The two PARPi tested then appear to modulate the choice of fork restart mechanisms and influence replisome dynamics in different ways. Taken together, our study highlights the common and unique primary effects of two PARPi on unperturbed DNA replication in human cells. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=169 SRC="FIGDIR/small/639283v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@298f8dorg.highwire.dtl.DTLVardef@8f8cbcorg.highwire.dtl.DTLVardef@60952forg.highwire.dtl.DTLVardef@e2700a_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2022

Palbociclib interferes with replication origin firing in a pRb independent manner

Over the last decade, CDK4/6 inhibitors (palbociclib, ribociclib and abemaciclib) have emerged as promising anticancer drugs. Numerous studies have demonstrated that CDK4/6 inhibitors efficiently block the pRb-E2F pathway and induce cell cycle arrest in pRb-proficient cells. Based on these studies, the inhibitors have been approved by the FDA for treatment of advanced hormonal receptor (HR) positive breast cancers in combination with hormonal therapy. However, some evidence has recently shown unexpected effects of the inhibitors, promoting needs to understand more about the mechanism of inhibitors beyond pRb. Our study demonstrates here how palbociclib impairs the origin firing in the DNA replication process in pRb-deficient cell lines. Strikingly, despite the absence of pRb, cells treated with palbociclib synthesize less DNA without any induced cell cycle arrest. Furthermore, palbociclib treatment disturbs the temporal program of DNA replication and reduces the density of replication forks. Cells treated with palbociclib show a defect in the loading of proteins of the Pre-initiation complex (Pre-IC) on chromatin, indicating a reduced initiation of DNA replication. Our findings highlight hidden effects of palbociclib on the dynamics of DNA replication and on its cytotoxic consequences on cell viability in the absence of pRb. This study provides a potential therapeutic application of palbociclib to target genomic instability towards pRb deficient patients. Significance StatementPalbociclib is a promising anticancer drug for pRb-proficient cell, particularly for hormonal receptor positive breast cancer, that induces the cell cycle arrest. But what about pRb deficient cell lines ? Our results show that Palbociclib disturb the DNA replication process inducing a replicative stress, an increase of DNA damages and leading to a significant decrease in cell viability. Palbociclib impairs the DNA synthesis reducing the number of active origins with the decrease of availability of the pre-initiation complexes. We believe that the demonstration of this effect of palbociclib on pRb-deficient cells may be a new therapeutic entry point in combination with other treatments for these types of cancer. Replicative stress can be one of weaknesses of pRb defficient cancer cells.

cancer biology↗

bioRxiv2019

New, easy, quick and efficient DNA replication timing analysis by high-throughput approaches.

DNA replication must be faithful and follow a well-defined spatio-temporal program closely linked to transcriptional activity, epigenomic marks, intra-nuclear structures, mutation rate and cell fate determination. Among the readouts of the DNA replication spatio-temporal program, replication timing (RT) analyses require complex, precise and time-consuming experimental procedures, and the study of large-size computer files. We improved the RT protocol to speed it up and increase its quality and reproducibility. Also, we partly automated the RT protocol and developed a user-friendly software: the START-R suite (Simple Tool for the Analysis of the Replication Timing based on R). START-R suite is an open source web application using an R script and an HTML interface to analyze DNA replication timing in a given cell line with microarray or deep-sequencing results. This novel approach can be used by every biologist without requiring specific knowledge in bioinformatics. It also reduces the time required for generating and analyzing simultaneously data from several samples. START-R suite detects constant timing regions (CTR) but also, and this is a novelty, it identifies temporal transition regions (TTR) and detects significant differences between two experimental conditions. The informatic global analysis requires less than 10 minutes.

genomics↗