Biology subjects

Vieira, H. G. S.

Publications and source records attributed to Vieira, H. G. S..

4 recordsLinked to original sources

bioRxiv2025

High-content imaging reveals the ability of microexons to shape protein localisation

Alternative splicing provides a pervasive means to expand proteome complexity, yet how it reorganises protein interactions and constrains where proteins act within cell remains unclear. By constructing an interface-resolved interaction network composed of 17,660 experimentally defined contact sites, we reveal that tissue-specific alternative splicing remodels protein connectivity by reshaping modular protein architecture. Longer exons reshape local interaction patterns whereas microexons fine-tune key interfaces linking distinct cellular processes. Integration of subcellular localisation data further indicates that such rewiring can redistribute proteins within cells. To test this, we developed a high-content imaging approach to systematically evaluate the influence of individual exons on protein localisation and screened a targeted library of protein isoforms differing in individual exons. 38% of the tested isoform pairs altered localisation, with microexons, although typically shorter than five amino acids, accounting for a substantial proportion of these effects. Bioinformatic and structural analyses identified that microexons can extend secondary structural regions and reposition charged residues, suggesting a potential to modulate local electrostatic environments. Consistent with this, biochemical analysis of a four-amino acid microexon in sorting nexin 2 - identified through our screen - confirmed that residue insertion, rather than side chain chemistry, was driving differences in protein localisation through repositioning of a flanking, charged residue. Together, these findings describe a principle by which alternative splicing fine-tunes interface architecture to coordinate protein assembly, localisation, and proteome organisation.

molecular biology↗

bioRxiv2025

Isoform-specific single-cell perturb-seq reveals distinct functions of alternative promoters in drug response

CRISPR interference (CRISPRi) screens have emerged as powerful tools for dissecting gene function, yet their application to genes with multiple promoters, which comprise over 60% of human genes, remains poorly understood. Here, we demonstrate that CRISPR-dCas9-based screens exhibit widespread promoter specificity, with untargeted promoters often showing compensatory upregulation to maintain gene expression. Leveraging this selective targeting of individual promoters within the same gene, we developed isoform-specific single-cell Perturb-Seq to systematically analyse alternative promoter function. Our analysis revealed that alternative promoters in 48.3% of targeted genes drive distinct transcriptional programs. This suggests that promoter selection represents a fundamental mechanism for generating cellular diversity rather than mere transcriptional redundancy. In breast cancer models, this promoter-specific targeting revealed differential effects on drug sensitivity, where distinct estrogen receptor (ESR1) promoters showed opposing influences on tamoxifen response and patient survival. These findings demonstrate the necessity of promoter-level analysis in functional genomics and suggest new strategies for therapeutic intervention through promoter-specific targeting.

genomics↗

bioRxiv2020

Subcellular relocalization and nuclear redistribution of the RNA methyltransferases TRMT1 and TRMT1L upon neuronal activation

RNA modifications are dynamic chemical entities that regulate RNA fate, and an avenue for environmental response in neuronal function. However, which RNA modifications may be playing a role in neuronal plasticity and environmental responses is largely unknown. Here we characterize the biochemical function and cellular dynamics of two human RNA methyltransferases previously associated with neurological dysfunction, TRMT1 and its homolog, TRMT1-like (TRMT1L). Using a combination of next-generation sequencing, LC-MS/MS, patient-derived cell lines and knockout mouse models, we confirm the previously reported dimethylguanosine (m 2,2 G) activity of TRMT1 in tRNAs, as well as reveal that TRMT1L, whose activity was unknown, is responsible for methylating a subset of cytosolic tRNA Ala (AGC) isoacceptors at position 26. Using a cellular in vitro model that mimics neuronal activation and long term potentiation, we find that both TRMT1 and TRMT1L change their subcellular localization upon neuronal activation. Specifically, we observe a major subcellular relocalization from mitochondria and other cytoplasmic domains (TRMT1) and nucleoli (TRMT1L) to different small punctate compartments in the nucleus, which are as yet uncharacterized. This phenomenon does not occur upon heat shock, suggesting that the relocalization of TRMT1 and TRMT1L is not a general reaction to stress, but rather a specific response to neuronal activation. Our results suggest that subcellular relocalization of RNA modification enzymes play a role in neuronal plasticity and transmission of information, presumably by addressing new targets.

molecular biology↗

bioRxiv2020

Decoding ribosomal RNA modification dynamics at single molecule resolution

A broad diversity of modifications decorate RNA molecules. Originally conceived as static components, evidence is accumulating that some RNA modifications may be dynamic, contributing to cellular responses to external signals and environmental circumstances. A major difficulty in studying these modifications, however, is the need of tailored protocols to map each modification type individually. Here, we present a new approach that uses direct RNA nanopore sequencing to identify and quantify RNA modifications present in native RNA molecules. First, we show that each RNA modification type results in a distinct and characteristic base-calling error signature, which we validate using a battery of genetic strains lacking either pseudouridine (Y) or 2-O-methylation (Nm) modifications. We then demonstrate the value of these signatures for de novo prediction of Y modifications transcriptome-wide, confirming known Y-modified sites as well as uncovering novel Y sites in mRNAs, ncRNAs and rRNAs, including a previously unreported Pus4-dependent Y modification in yeast mitochondrial rRNA, which we validate using orthogonal methods. To explore the dynamics of pseudouridylation across environmental stresses, we treat the cells with oxidative, cold and heat stresses, finding that yeast ribosomal rRNA modifications do not change upon environmental exposures, contrary to the general belief. By contrast, our method reveals many novel heat-sensitive Y-modified sites in snRNAs, snoRNAs and mRNAs, in addition to recovering previously reported sites. Finally, we develop a novel software, nanoRMS, which we show can estimate per-site modification stoichiometries from individual RNA molecules by identifying the reads with altered current intensity and trace profiles, and quantify the RNA modification stoichiometry changes between two conditions. Our work demonstrates that Y RNA modifications can be predicted de novo and in a quantitative manner using native RNA nanopore sequencing.

molecular biology↗