Biology subjects

Viennet, T.

Publications and source records attributed to Viennet, T..

6 recordsLinked to original sources

bioRxiv2025

Biosynthesis, Structure, and Antibiotic Properties of Gelatinamin A, a Triculamin-like Lasso Peptide

Lasso peptides are structurally unique natural products endowed with high thermal and proteolytic stability, making them attractive as scaffolds for drug discovery. Recently, a new class of lasso peptides containing a second macrocycle, formed between a lysine sidechain and the C-terminus, was discovered, resulting in an even more compact architecture. Here, we report the first NMR structure of the class V lasso peptide, gelatinamin A. Using heterologous expression of the gelatinamin biosynthetic gene cluster (BGC) in Bacillus subtilis, we delineated the biosynthetic pathway through targeted gene deletions. We expressed and characterized the predicted transpeptidase, GelP, that catalyzes the formation of an isopeptide bond between Lys2 and the C-terminus and mediates the reversible conversion of gelatinamin B to gelatinamin A. In addition, we characterize GelT, an N-acetyltransferase that inactivates lasso peptide antimicrobial activity by acetylating a key lysine residue. Furthermore, we demonstrate that gelatinamin is highly potent against several important pathogens and that the activity is strongly bicarbonate-dependent. Finally, we propose a complete biosynthetic pathway for gelatinamin. The structural insight of gelatinamin A and the functional characterization of GelP provide the foundation for future discovery of class V lasso peptides and for engineering transpeptidases to modify other lasso peptide scaffolds.

biochemistry↗

bioRxiv2025

FoxP3 forms a head-to-head dimer in vivo and stabilizes its multimerization on adjacent microsatellites

FoxP3, the master regulator of Tregs, employs two DNA-binding modes to recognize diverse DNA sequences. It multimerizes on long TnG repeats (n = 2-5) to bridge DNA segments and stabilize chromatin loops, and it forms head-to-head (H-H) dimers on inverted repeat forkhead motifs (IR-FKHM) without bridging DNA. Although genomic data confirm its multimeric role, in vivo evidence for H-H dimerization has been elusive. Here, unbiased pull-down sequencing uncovers a range of relaxed motifs that drive H-H dimerization, enabling systematic genome- wide analysis. We demonstrate that FoxP3 binds genomic DNA as both H-H dimers and multimers in Tregs, with H-H binding often seeding and stabilizing multimerization on adjacent TnG repeats--especially on shorter, suboptimal repeats. While multimerization is conserved across FoxP family members, H-H dimerization is unique to FoxP3 orthologs, conferred by its divergent accessory loop. This dual-mode strategy broadens FoxP3s sequence repertoire and enhances its architectural function in chromatin looping.

bioinformatics↗

bioRxiv2024

Structural Insights into the DNA-Binding Mechanism of BCL11A: The Integral Role of ZnF6

The transcription factor BCL11A is a critical regulator of the switch from fetal hemoglobin (HbF: 2{gamma}2) to adult hemoglobin (HbA: 2{beta}2) during development. BCL11A binds at a cognate recognition site (TGACCA) in the {gamma}-globin gene promoter and represses its expression. DNA-binding is mediated by a triple zinc finger domain, designated ZnF456. Here, we report comprehensive investigation of ZnF456, leveraging X-ray crystallography and NMR to determine the structures in both the presence and absence of DNA. We delve into the dynamics and mode of interaction with DNA. Moreover, we discovered that the last zinc finger of BCL11A (ZnF6) plays a special role in DNA binding and {gamma}-globin gene repression. Our findings help account for some rare {gamma}-globin gene promoter mutations that perturb BCL11A binding and lead to increased HbF in adults (hereditary persistence of fetal hemoglobin). Comprehending the DNA binding mechanism of BCL11A opens avenues for the strategic, structure-based design of novel therapeutics targeting sickle cell disease and {beta}-thalassemia.

molecular biology↗

bioRxiv2022

MIADE metadata guidelines: Minimum Information About a Disorder Experiment

An unambiguous description of an experimental setup and analysis, and the subsequent biological observation is vital for accurate data interpretation and reproducible results. Consequently, experimental analyses should be described in a concise, unequivocal, and digestible manner. The aim of minimum information guidelines is to define the fundamental complement of data that can support an unambiguous conclusion on experimental observations. In this document, we present the Minimum Information About Disorder Experiments (MIADE) guidelines to define the minimal fundamental parameters required for non-experts to understand the key findings of an experiment studying intrinsically disordered proteins (IDPs) or intrinsically disordered protein regions (IDRs). MIADE guidelines provide recommendations for data producers to describe the results of their experiments at source, for curators to annotate experimental data to community resources and for database developers maintaining community resources to disseminate the data. We give examples of the application of these guidelines in common use cases and describe the implementation of an update to the DisProt IDP database to allow MIADE-compliant annotation. The MIADE guidelines will improve the interpretability of experimental results for data consumers, facilitate direct data submission, simplify data curation, improve data exchange among repositories and standardise the dissemination of the key metadata on an IDP experiment by IDP data sources.

scientific communication and education↗

bioRxiv2022

PH Domain-Mediated Autoinhibition and Oncogenic Activation of Akt

Previously, we reported that the conformation of autoinhibited Akt, a Ser/Thr protein kinase that plays a central role in metabolism and cancer, may be shifted by small molecule allosteric inhibitors limiting the mechanistic insights from existing X-ray structures that have relied on such compounds (Chu, Viennet, et al, 2020). Here we discover unexpectedly that a single mutation, R86A, in Akts PH domain exhibits intensified autoinhibitory features with enhanced PH domain-kinase domain affinity. Structural and biochemical analysis uncovers the importance of a key interaction network involving Arg86, Glu17, and Tyr18 that controls Akt conformation and activity. Our studies also shed light on the molecular basis for E17K Akt activation as an oncogenic driver.

biochemistry↗

bioRxiv2017

A structural and kinetic link between membrane association and amyloid fibril formation of α-Synuclein

The protein -Synuclein (S) is linked to Parkinsons disease through its abnormal aggregation, which is thought to involve an interplay between cytosolic and membrane-bound forms of S. Therefore, better insights into the molecular determinants of membrane association and their implications for protein aggregation may help deciphering the pathogenesis of Parkinsons disease. Following previous studies using micelles and vesicles, we present a comprehensive study of S interaction with phospholipid bilayer nanodiscs. Using a combination of NMR - spectroscopic and complementary biophysical as well as computational methods we structurally and kinetically characterize S interaction with defined stable planar membranes in a quantitative and site-resolved way. We probe the role of S acetylation as well as membrane charge, plasticity and available surface area in modulating S membrane binding modes and directly link these findings to their consequences for S amyloid fibril formation.

biophysics↗