La Manna, S. | bioRxiv Science

bioRxiv2025

A self-assembling cross-protective antigen against multiple Gram-positive nosocomial pathogens

ESKAPE pathogens are responsible for complicated nosocomial infections worldwide and are usually resistant to commonly used antibiotics in clinical settings. Among these bacteria, vancomycin-resistant Enterococcus faecium and methicillin-resistant Staphylococcus aureus are the two most important Gram-positive pathogens for which alternative treatments and preventions are urgently needed. We previously designed a multi-presenting antigen, embedding the main epitope displayed by the AdcA protein of E. faecium, that conferred protection against different Gram- positive pathogens both in passive and active immunization models. Here, we developed a new presentation strategy for this epitope, the EH-motif, based on a self-assembling peptide. Self- assembling peptides have been promising in the fields of material sciences, nanoscience, and medicine and have also potential in vaccine development, as they allow multiple presentations of the epitope and provide an ideal size for production and application. We show that this multi- presenting peptide, here Q11-EH, forms stable fibers of nanometric size. We also demonstrate that antibodies raised against Q11-EH mediate the opsonic killing of a wide-spectrum of Gram-positive pathogens, including E. faecium, S. aureus, and E. faecalis. Our data indicate that multiple presentation strategies are a potent tool for vaccine antigen improvement and point to Q11-EH as a promising antigen for the development of novel cross-protective vaccines.

immunology↗

bioRxiv2024

The Apurinic/Apyrimidinic Endodeoxyribonuclease 1 is an RNA G-quadruplex binding protein and regulates miR-92b expression in cancer cells

In the last decade, several novel functions of the mammalian Apurinic/Apyrimidinic Endodeoxyribonuclease 1 (APE1) have been discovered, going far beyond its canonical function as a DNA repair enzyme, unveiling its potential roles in cancer development. Indeed, it was shown to be involved in DNA G-quadruplex biology and RNA metabolism, most importantly in the miRNA maturation pathway and the decay of oxidized- or abasic-miRNAs during oxidative stress conditions. Furthermore, in recent years several non-canonical pathways of miRNA biogenesis have been described, with a specific focus on guanosine-rich precursors that can form RNA G-quadruplex (rG4) structures. In this study, we show that several miRNA precursors, dysregulated upon APE1-depletion, contain an rG4 motif and that their corresponding target genes are upregulated after APE1-depletion. We also show, both by in vitro assays and by using a HeLa cell model, that APE1 can bind and regulate the folding of an rG4 structure contained in pre-miR92b, with a mechanism strictly dependent on critical lysine residues present in the N-terminal disordered region. Furthermore, APE1 depletion in HeLa cells alters the maturation process of miR-92b, mainly affecting the shuttling between the nucleus and cytosol. Lastly, bioinformatic analysis of APE1-regulated rG4-containing miRNAs supports the relevance of our findings for cancer biology. Specifically, these miRNAs exhibit high prognostic significance in lung, cervical, and liver cancer, as suggested by their involvement in several cancer-related pathways. Significance StatementWe highlight an undescribed non-canonical role of the mammalian Apurinic/Apyrimidinic Endodeoxyribonuclease 1 (APE1) in the context of RNA G-quadruplexes (rG4), specifically in the alternative pathway of miRNA maturation of guanosine-rich miRNA precursors. Specifically, APE1 binds these structures and modulates their folding, mainly through its N-terminal region and some residues in its catalytic domain. Moreover, we showed an interesting new role of APE1 in regulating the shuttling and accumulation of miR-92b between the nuclear and cytosolic compartments, opening new perspectives on how APE1 may exercise its role in the miRNA maturation pathway and function. Moreover, APE1-depleted dysregulated miRNAs with rG4 motifs in their precursors have significant prognostic value in lung, cervical, and liver tumors, suggesting potential targets for cancer therapy.

molecular biology↗