Biology subjects

Aguilera, A.

Publications and source records attributed to Aguilera, A..

23 records · Page 2Linked to original sources

bioRxiv2020

Harmful DNA:RNA hybrids are formed in cis and in a Rad51-independent manner

DNA:RNA hybrids constitute a well-known source of recombinogenic DNA damage. The current literature is in agreement with DNA:RNA hybrids being produced co-transcriptionally by the invasion of the nascent RNA molecule produced in cis with its DNA template. However, it has also been suggested that recombinogenic DNA:RNA hybrids could be facilitated by the invasion of RNA molecules produced in trans in a Rad51-mediated reaction. Here, we tested the possibility that such DNA:RNA hybrids produced in trans constitute a source of recombinogenic DNA damage taking advantage of Rad51-independent single-strand annealing recombination assays and new constructs designed to induce expression of mRNA transcripts in trans in the yeast Saccharomyces cerevisiae. We show that unscheduled and recombinogenic DNA:RNA hybrids are formed in cis during transcription and in a Rad51-independent manner.

molecular biology↗

bioRxiv2019

APOBEC3A Catalyzes Mutation and Drives Carcinogenesis In Vivo

The APOBEC3 family of antiviral DNA cytosine deaminases is implicated as the second largest source of mutation in cancer. This mutational process may be a causal driver or inconsequential passenger to the overall tumor phenotype. We show that human APOBEC3A expression in murine colon and liver tissues increases tumorigenesis. All other APOBEC3 family members including APOBEC3B did not as strongly promote liver tumor formation. DNA sequences from APOBEC3A-expressing animals display hallmark APOBEC signature mutations in TCA/T motifs. Bioinformatic comparisons of the observed APOBEC3A mutation signature in murine tumors, previously reported APOBEC3A and APOBEC3B mutation signatures in yeast, and reanalyzed APOBEC mutation signatures in human tumor data sets support cause-and-effect relationships for APOBEC3A-catalyzed deamination and mutagenesis in driving multiple human cancers.

cancer biology↗

bioRxiv2019

Heat stress induces ferroptosis in a photosynthetic prokaryote.

Ferroptosis is an oxidative iron-dependent form of cell death recently described in eukaryotic organisms like animals, plants and parasites. Here we report that a similar process takes place in the cyanobacterium Synechocystis sp. PCC 6803 in response to heat stress. After a heat shock, Synechocystis cells undergo a cell death pathway that can be suppressed by canonical ferroptosis inhibitors or by external addition of calcium, glutathione or ascorbic acid. Moreover, as described for eukaryotic cells ferroptosis, this pathway is characterized by an early depletion of antioxidants, and by lipid peroxidation. As in general prokaryotes membranes contain poorly oxidizable saturated or monounsaturated lipid molecules, it was thought that they were not susceptible to ferroptosis. Interestingly, cyanobacteria contain thylakoid membranes that are enriched in polyunsaturated-fatty-acid-containing phospholipids, which might explain their sensitivity to ferroptosis. These results indicate that all of the hallmarks described for eukaryotic ferroptosis are conserved in photosynthetic prokaryotes and suggest that ferroptosis might be an ancient cell death program.\n\nSummaryAguilera et al, show that ferroptosis, an oxidative and iron-dependent form of regulated cell death, plays an important role in the cyanobacterium Synechocystis sp. PCC 6803 in response to heat stress.

microbiology↗

bioRxiv2019

A new role of the Mus81 nuclease for replication completion after fork restart

Impediments to DNA replication threaten genome stability. The homologous recombination (HR) pathway is involved in the restart of blocked replication forks. Here, we used a new method to study at the molecular level the restart of replication in response to DNA topoisomerase I poisoning by camptothecin (CPT). We show that HR-mediated restart at the global genomic level occurs by a BIR-like mechanism that requires Rad52, Rad51 and Pol32. The Mus81 endonuclease, previously proposed to cleave blocked forks, is not required for replication restart in S phase but appears to be essential to resolve fork-associated recombination intermediates in G2/M as a step necessary to complete replication. We confirmed our results using an independent system that allowed us to conclude that this mechanism is independent of the accumulation of DNA supercoiling and DNA-protein crosslinks normally caused by CPT. Thus, we describe here a specific function for Mus81 in the processing of HR-restarted forks required to complete DNA replication.

molecular biology↗

bioRxiv2018

DDX41 recognizes RNA/DNA retroviral reverse transcripts and is critical for in vivo control of MLV infection

Host recognition of viral nucleic acids generated during infection leads to the activation of innate immune responses essential for early control of virus. Retrovirus reverse transcription creates numerous potential ligands for cytosolic host sensors that recognize foreign nucleic acids, including single-stranded RNA (ssRNA), RNA/DNA hybrids and double stranded DNA (dsDNA). We and others recently showed that the sensors cyclic GMP-AMP synthase (cGAS), dead-box helicase 41 (DDX41) and members of the Aim2-like receptor (ALR) family participate in the recognition of retroviral reverse transcripts. However, why multiple sensors might be required and their relative importance in in vivo control of retroviral infection is not known. Here we show that DDX41 primarily senses the DNA/RNA hybrid generated at the first step of reverse transcription, while cGAS recognizes dsDNA generated at the next step. We also show that both DDX41 and cGAS are needed for the anti-retroviral innate immune response to MLV and HIV in primary mouse macrophages and dendritic cells (DC). Using mice with macrophage- or -specific knockout of the DDX41 gene, we show that DDX41 sensing in DCs but not macrophages was critical for controlling in vivo MLV infection. This suggests that DCs are essential in vivo targets for infection, as well as for initiating the antiviral response. Our work demonstrates that the innate immune response to retrovirus infection depends on multiple host nucleic acid sensors that recognize different reverse transcription intermediates.\n\nImportanceViruses are detected by many different host sensors of nucleic acid, which in turn trigger innate immune responses, such as type I IFN production, required to control infection. We show here that at least two sensors are needed to initiate a highly effective innate immune response to retroviruses - DDX41, which preferentially senses the RNA/DNA hybrid generated at the first step of retrovirus replication and cGAS, which recognizes double-stranded DNA generated at the 2nd step. Importantly, we demonstrate using mice lacking DDX41 or cGAS, that both sensors are needed for the full antiviral response needed to control in vivo MLV infection. These findings underscore the need for multiple host factors to counteract retroviral infection.

microbiology↗