Biology subjects

Pozzi, B.

Publications and source records attributed to Pozzi, B..

5 recordsLinked to original sources

bioRxiv2026

Targeting CLK1 by CRISPR tools and pharmacological inhibition modulates the innate immune response and dengue virus replication

Alternative splicing is a key regulatory mechanism known to be altered upon viral infection. These alterations can arise both from direct viral interference with the splicing machinery and from cellular responses such as activation of innate immunity. Here, we investigated splicing changes shared between dengue virus (DENV) infection and interferon (IFN) treatment in cultured cells, the latter serving as a model for virus-independent innate immune activation. Among the common events, we identified an increased production of non-coding mRNA isoforms from the CLK1 gene, which gives rise to a kinase that phosphorylates splicing factors including SR proteins and spliceosomal components. Consistent with this finding, IFN treatment led to a reduction in CLK1 protein levels. Using stable cell lines with CRISPR/dCas9-mediated modulation of CLK1 expression, we found that silencing CLK1 enhanced the induction of immune response genes, while its over-expression attenuated it. Inhibition of CLK1 kinase activity with the pharmacological inhibitor TG003 further potentiated IFN-induced gene expression and reduced DENV replication. Altogether, these results identify CLK1 as a proviral negative regulator of IFN-stimulated gene expression and suggest that its inhibition could enhance antiviral defenses and become a target for therapeutic strategies.

molecular biology↗

bioRxiv2025

Differential contribution of the RNA recognition motifs to SRSF1 protein interaction network

The protein SRSF1, initially identified as a splicing factor, is currently known to participate in a variety of cellular processes. However, its role and regulatory mechanisms in these processes remain incompletely understood. Using a SILAC proteomic approach, we have characterised the SRSF1 interactome, thereby identifying multiple diverse protein interaction partners of SRSF1 and the molecular complexes with which it is associated. Given that the RNA-binding ability of SRSF1 is necessary for many of its activities, we extended the analysis of the SRSF1 interactome to compare the wild type protein against two site-specific SRSF1 variants, bearing mutations in each of its two RNA recognition motifs (RRMs). The first mutation disrupted the canonical RRM (RRM1), while the second affected the pseudo-RRM (RRM2). Interestingly, the data show clear differences between the SRSF1 interacting proteins, depending on the functional status of each RRM domain. In particular, a functional RRM1 was critical for maintaining interactions with multiple partners, especially those involved in translation-related processes, showing a far greater loss of interactions upon mutation than RRM2. This study provides valuable new insights into the broader cellular roles and interaction landscape of SRSF1.

molecular biology↗

bioRxiv2022

Influence of circular RNA topology on microRNA stability

A subset of circular RNAs (circRNAs) and linear RNAs have been proposed to "sponge" or block microRNA activity. Additionally, certain RNAs induce microRNA destruction through the process of Target RNA-Directed MicroRNA Degradation (TDMD), but whether both linear and circular transcripts are equivalent in driving TDMD is unknown. Here we study whether circular/linear topology of endogenous and artificial RNA targets affects TDMD. Consistent with previous knowledge that Cdr1as (ciRS-7) circular RNA protects miR-7 from Cyrano-mediated TDMD, we demonstrate that depletion of Cdr1as reduces miR-7 abundance. In contrast, overexpression of an artificial linear version of Cdr1as drives miR-7 degradation. Using plasmids that express a circRNA with minimal co-expressed cognate linear RNA, we show differential effects on TDMD that cannot be attributed to the nucleotide sequence, as the TDMD properties of a sequence often differ between its circular and linear forms. By analysing RNA sequencing data of a neuron differentiation system, we further detect potential effects of circRNAs on microRNA stability. Our results support the view that RNA circularity influences TDMD, either enhancing or inhibiting it on specific microRNAs.

molecular biology↗

bioRxiv2022

SUMO conjugation regulates the activity of the Integrator complex

RNA pol II transcribes snRNA genes in close proximity to Cajal bodies, subnuclear compartments that depend on the SUMO isopeptidase USPL1 for their assembly. We show here that overexpression of USPL1 alters snRNA 3-end cleavage, a process carried out by the Integrator complex. Beyond its role in snRNA biogenesis, this complex is responsible for regulating the expression of different non-coding and coding transcripts. We validated several subunits of the complex as SUMO conjugation substrates, and found that the SUMOylation of INTS11 subunit is regulated by USPL1. We defined Lys 381, Lys 462 and Lys 475 as bona fide SUMO attachment sites within INTS11 and observed that SUMOylation of this protein is required for efficient Integrator activity. Moreover, while an INTS11 SUMOylation deficient mutant is still capable of interacting with INTS4 and INTS9, its interaction with other subunits of the complex is affected. This mutant also shows a more cytoplasmatic localization than the wild type protein. These findings point to a regulatory role of SUMO conjugation on Integrator activity and suggest the involvement of INTS11 SUMOylation in the assembly of the complex. Furthermore, this work adds the Integrator-dependent RNA processing to the growing list of cellular processes regulated by SUMO conjugation.

molecular biology↗

bioRxiv2020

SARS-CoV-2 spike D614G variant confers enhanced replication and transmissibility

During the evolution of SARS-CoV-2 in humans a D614G substitution in the spike (S) protein emerged and became the predominant circulating variant (S-614G) of the COVID-19 pandemic1. However, whether the increasing prevalence of the S-614G variant represents a fitness advantage that improves replication and/or transmission in humans or is merely due to founder effects remains elusive. Here, we generated isogenic SARS-CoV-2 variants and demonstrate that the S-614G variant has (i) enhanced binding to human ACE2, (ii) increased replication in primary human bronchial and nasal airway epithelial cultures as well as in a novel human ACE2 knock-in mouse model, and (iii) markedly increased replication and transmissibility in hamster and ferret models of SARS-CoV-2 infection. Collectively, our data show that while the S-614G substitution results in subtle increases in binding and replication in vitro, it provides a real competitive advantage in vivo, particularly during the transmission bottle neck, providing an explanation for the global predominance of S-614G variant among the SARS-CoV-2 viruses currently circulating.

microbiology↗