Biology subjects

Checa-Rodriguez, C.

Publications and source records attributed to Checa-Rodriguez, C..

3 recordsLinked to original sources

bioRxiv2023

RNA Polymerase II-mediated transcription is required for repair of ribosomal DNA breaks in nucleolar caps, guarding against genomic instability

Ribosomal DNA (rDNA) double-strand breaks (DSBs) threaten genome integrity due to the repetitive and transcriptionally active nature of rDNA. The nucleolus, while central to ribosome biogenesis, also functions as stress sensor. Here, we identify a transcription-dependent mechanism in which RNA polymerase II (RNAPII) is essential for homologous recombination (HR) repair of rDNA DSBs. Using CRISPR-induced breaks, high-resolution imaging, and transcriptional inhibition, we show that RNAPII activity drives the formation of nucleolar repair caps. Mechanistically, CtIP promotes RNAPII recruitment and H3K36 trimethylation at rDNA lesions, facilitating HR. Disruption of this RNAPII-CtIP-H3K36me3 axis impairs cap formation and repair, leading to persistent damage. RNAPII inhibition exacerbates genome instability and synergizes with rDNA breaks to induce cancer cell death, without acutely impairing ribosome function. These findings uncover a co-transcriptional mechanism of rDNA repair and highlight RNAPII-mediated chromatin remodeling and spatial reorganization as key to nucleolar genome maintenance and potential targets for cancer therapy. TeaserNascent RNA synthesis by RNAPII safeguards ribosomal DNA integrity to avoid genomic instability in human cells. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=137 HEIGHT=200 SRC="FIGDIR/small/563274v2_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@8e9b03org.highwire.dtl.DTLVardef@63116eorg.highwire.dtl.DTLVardef@d583dorg.highwire.dtl.DTLVardef@1c2eab_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2023

Human Cryptochrome1 dampens homologous recombination at nightfall

Genomic stability maintenance requires the repair of DNA breaks in the most accurate fashion. So, an exquisite regulatory network controls the choice between different repair mechanisms to maximize genome integrity. This relies mostly at the level of DNA end resection, the initial steps of the homologous recombination. On the other hand, numerous cellular activities follow a 24 h oscillation known as the circadian cycle. Thus, we explored the regulation of the choice between different DNA break repair pathways along the circadian cycle. Here we show that in human cells DNA resection shows a circadian oscillation, with a peak at early morning followed by a partial and progressive reduction until late afternoon. Such regulation depends on the circadian clock core component CRY1, which modulates the anti-resection activity of CCAR2 to limit CtIP at nightfall. Additionally, such regulation requires DNA-PK-mediated phosphorylation of CRY1. Finally, this circadian regulation impacts cancer progression and response to radiation therapy of specific tumours.

cell biology↗

bioRxiv2019

PHF2 regulates homology-directed DNA repair by controlling the resection of DNA double strand breaks

Post-translational histone modifications and chromatin remodelling play a critical role in the mechanisms controlling the integrity of the genome. Here we identify histone lysine demethylase PHF2 as a novel regulator of the DNA damage response by regulating the balance between DNA damage-induced focus formation by 53BP1 and BRCA1, critical factors in the pathway choice for DNA double strand break repair. PHF2 knock down leads to impaired BRCA1 focus formation and delays the resolution of 53BP1 foci. Moreover, irradiation-induced RPA phosphorylation and focus formation, as well as localization of CtIP, required for DNA end resection, to sites of DNA lesions are affected by depletion of PHF2. These results are indicative of a defective resection of double strand breaks and thereby an impaired homologous recombination upon PHF2 depletion. In accordance with these data, Rad51 focus formation and homology-directed double strand break repair is inhibited in cells depleted for PHF2. Importantly, we demonstrate that PHF2 knock down decreases CtIP and BRCA1 protein and mRNA levels and cells depleted of PHF2 display genome instability and are sensitive to the inhibition of PARP. Together these results demonstrate that PHF2 promotes DNA repair by homologous recombination by controlling CtIP-dependent resection of double strand breaks.

molecular biology↗