Biology subjects

Manfredi, L.

Publications and source records attributed to Manfredi, L..

3 recordsLinked to original sources

bioRxiv2025

Ischemic stroke increases levels of the folate receptor and one-carbon enzymes in male and female brain tissue

Stroke is the second most common cause of death worldwide and predominantly affects individuals over 65 years old. Its prevalence is projected to increase in parallel with the aging global population. Nutrition is a modifiable risk factor for ischemic stroke. Folates, B-vitamins and choline play a central role in one-carbon metabolism (1C), which is a key metabolic network that integrates nutritional signals with biosynthesis, redox homeostasis, epigenetics, regulation of cell proliferation, and stress resistance. Our research group has previously shown that deficiencies in 1C lead to worsened stroke outcomes using preclinical models. However, the impact of ischemic stroke on 1C enzymes in affected brain tissue remains unknown. The objective of this study is to investigate whether ischemic stroke contributes to a change in the levels of 1C enzymes after ischemic stroke in male and female patients. Cortical brain tissue sections from ischemic stroke patients and controls were stained for enzymes involved in 1C. All tissue was co-stained with neuronal nuclei (NeuN) and DAPI (4',6-diamidino-2-phenylindole). The colocalization of all three markers was evaluated by two individuals who were blinded to the experimental groups. Ischemic stroke increased neuronal levels of the folate receptor and 1C enzymes, methylenetetrahydrofolate reductase (MTHFR), thymidylate synthase (TS) and serine hydroxy methyltransferase (SHMT). In male stroke brain tissue was observed to have increased levels of MTHFR, TS, and SHMT. Female brain tissue had increases in the folate receptor and TS. The results suggest that ischemic stroke leads to increased demand of 1C and that there are some differences between males and females. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=92 SRC="FIGDIR/small/673861v1_ufig1.gif" ALT="Figure 1"> View larger version (12K): org.highwire.dtl.DTLVardef@18e7c60org.highwire.dtl.DTLVardef@187a339org.highwire.dtl.DTLVardef@1ed0568org.highwire.dtl.DTLVardef@1fdfe31_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2024

DROSHA, DICER and Damage-Induced long ncRNA control BMI1-dependent transcriptional repression at DNA double-strand break

Genome integrity is safeguarded by the DNA damage response (DDR). Controlled transcriptional dampening of genes surrounding DNA double-strand breaks (DSBs) has been shown to facilitate DNA repair. This phenomenon, defined as DSB-induced silencing in cis (DISC), involves the DDR apical kinase ATM and the Polycomb Repressive Complex 1 (PRC1). Conversely, DSBs have also been reported to induce de novo transcription of damaged-induced long non-coding RNAs (dilncRNAs) in a MRE11-RAD50-NBS1 (MNR) complex-dependent manner. MRN also controls the recruitment to DSB of the ribonuclease DROSHA, which together with DICER, stimulates DDR signaling and DNA repair. Here, we reconcile these apparently contrasting observations by showing that dilncRNA, together with DROSHA and DICER, but not GW182-like proteins required for miRNA-mediated gene silencing, controls DISC. Indeed, similarly to ATM, MRN inhibition abolishes DISC while pharmacological enhancement of DICER ribonuclease activity by Enoxacin improves DISC. Importantly, Enoxacin administration restores DISC upon ATM inhibition, demonstrating that DICER promotes DISC independently from ATM. Differently, Enoxacin does not restore DISC upon MRN inhibition, suggesting that DICER acts downstream to dilncRNA biogenesis and DROSHA recruitment. Mechanistically, we show that DROSHA and DICER control the recruitment of the PRC1 component BMI1 at DSBs and the consequent H2A-K119 ubiquitination. Upon DSBs formation, BMI1 and DROSHA interact in an RNA-dependent manner. Indeed, BMI1 associates to dilncRNA and do so in a DROSHA- and DICER-dependent manner. Importantly, inhibition of dilncRNA function by antisense oligonucleotides or Cas13-mediated targeting is sufficient to reduce BMI1 recruitment and DISC at individual loci. We propose that dilncRNAs together with DROSHA and DICER control DISC at genomic DSB by supporting PRC1 recruitment and chromatin ubiquitination.

molecular biology↗

bioRxiv2024

The PIN1-p38-CtIP signaling axis protects stalled replication forks from deleterious degradation

Human CtIP plays a critical role in homologous recombination (HR) by promoting the resection of DNA double-strand breaks. Moreover, CtIP maintains genome stability through protecting stalled replication forks from nucleolytic degradation. However, the upstream signaling mechanisms governing the molecular switch between these two CtIP-dependent processes remain largely elusive. Here, we show that phosphorylation of CtIP by the p38 stress kinase and subsequent PIN1-mediated CtIP cis-to-trans isomerization is required for fork stabilization but dispensable for HR. We found that stalled forks are degraded in cells expressing non-phosphorylatable CtIP or lacking PIN1-p38 activity, while expression of a CtIP trans-locked mutant overcomes the requirement for PIN1-p38 in fork protection. We further reveal that Brca1-deficient mammary tumor cells that have acquired PARPi resistance regain chemosensitivity after PIN1 or p38 inhibition. Collectively, our findings identify the PIN1-p38-CtIP signaling pathway as a critical regulator of replication fork integrity.

molecular biology↗