Biology subjects

Maiorano, D.

Publications and source records attributed to Maiorano, D..

4 recordsLinked to original sources

bioRxiv2024

A non-catalytic function for Rad18 in sustaining glioblastoma proliferation

The Rad18 E3 ubiquitin ligase, a non-essential gene, is a key regulator of DNA damage tolerance that also functions in repair of DNA double strand breaks. Rad18 is overexpressed in the aggressive brain cancer glioblastoma (GBM) and its downregulation sensitizes glioblastoma cells to DNA damaging agents. Here we show that Rad18 has an essential role in GBM cells proliferation in the absence of external damage, surprisingly independent of its catalytic activity. Rad18 downregulation leads to cell cycle arrest in the G1 phase in the absence of apparent DNA damage. We also show that Rad18 sustains GBM stem cells self-renewal and survival, as well as the growth of tumor orthotropic xenografts in mice. We also show that increased Rad18 expression enhances the growth of non-transformed cells and induces features of oncogenic transformation. Mechanistically, we show that Rad18 downregulation negatively regulates the Hippo pathway by interfering with the nuclear retention of the YAP1 transcription factor. Altogether, these data show that Rad18 has an essential, non-catalytic function, in GBM proliferation, and propose Rad18 as a key target to sensitize GBM to therapy.

cancer biology↗

bioRxiv2023

Identification and Characterisation of Proteins Binding to a G-Quadruplex Origin G-rich Repeated Element in Mammalian Cells

In metazoan cells, replication of genomic DNA initiates from thousands of discrete chromosomal loci known as origins. Proteins such as the Origin Recognition Complex (ORCs) associate with origins, but this does not show clear sequence specificity for DNA binding. Genome-wide origin mapping studies have shown that the region surrounding the replication initiation site contains motifs such as the Origin G-rich Repeated Element (OGRE), proximal to the majority of origins. Here, using an approach coupling DNA affinity purification to quantitative proteomics, we identified proteins that interact specifically with an OGRE. Three of the top-scoring interactors, Dhx36, Pura and Tial1, were selected for further study. We show that Dhx36 and Tial1 localise to the nucleus and their knockdown decreased cells in S-phase resulting in their accumulation in the G1 phase of the cell cycle. Altogether these results indicate that these OGRE-binding factors may play roles in DNA synthesis in mammalian cells.

cell biology↗

bioRxiv2020

Translesion DNA synthesis-driven mutagenesis in very early embryogenesis of fast cleaving embryos

In early embryogenesis of fast cleaving embryos DNA synthesis is short and surveillance mechanisms preserving genome integrity are inefficient implying the possible generation of mutations. We have analyzed mutagenesis in Xenopus laevis and Drosophila melanogaster early embryos. We report the occurrence of a high mutation rate in Xenopus and show that it is dependent upon the translesion DNA synthesis (TLS) master regulator Rad18. Unexpectedly, we observed a homology-directed repair contribution of Rad18 in reducing the mutation load. Genetic invalidation of TLS in the pre-blastoderm Drosophila embryo resulted in reduction of both the hatching rate and Single Nucleotide Variations on specific chromosome regions in adult flies. Altogether, these findings indicate that during very early Xenopus and Drosophila embryos TLS strongly contributes to the high mutation rate. This may constitute a previously unforeseen source of genetic diversity contributing to the polymorphisms of each individual with implications for genome evolution and species adaptation.

developmental biology↗

bioRxiv2018

Dihydropyrimidinase protects from DNA replication stress caused by cytotoxic metabolites.

Metabolic alterations support cellular transformation. Noticeably, cellular transformation and cancer progression is associated with accumulation of dihydrouracil and dihydrothymine. However, it remains elusive how dihydropyrimidine metabolites affect cellular phenotypes. Dihydropyrimidines are degraded by dihydropyrimidinase (DHP). This zinc metalloenzyme is upregulated in solid tumors but not in the corresponding normal tissues. Here we show that DHP silencing in transformed cell lines is cytotoxic. Increasing the level of dihydropyrimidines inhibited DNA replication and transcription. It induced replication stress signaling by ATR and p53 stabilization. Remarkably, cells lacking DHP accumulated DNA-protein crosslinks (DPCs). Among DPCs, covalently trapped translesion DNA polymerase {eta} contributed to the cytotoxicity of dihydropyrimidines. Furthermore, we show that the plant flavonoid dihydromyricetin inhibits the activity of recombinant human DHP. Cellular treatment with dihydromyricetin triggered DPCs-dependent DNA replication stress. This study defines dihydropyrimidines as potentially cytotoxic metabolites that may offer an opportunity for therapeutic-targeting of DHP activity in solid tumors.

cancer biology↗