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DTSTART;TZID=Europe/Paris:20261127T110000
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DTSTAMP:20261104T201202Z
CREATED:20261104T201202Z
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UID:10000346-1795777200-1795780800@sfp-alpes.fr
SUMMARY:Carlos FERNANDES TORNERO (Biological Research Center | CSIC\, Madrid)
DESCRIPTION:RNA polymerases : transcription and beyond\nSéminaire conjoint des jeunes chercheurs de l’IBS et du PSB \nRésumé : \nRNA polymerases are large macromolecular assemblies that transcribe the genome in all organisms. Because RNA polymerases work on the chromatin\, their activity is connected to other cellular processes such as DNA repair and DNA integration. Eukaryotic RNA polymerases I and III (Pol I and Pol III) synthesize untranslated RNAs that mediate protein synthesis\, regulate gene activity or catalyze chemical reactions. In the talk\, Carlos Fernández-Tornero will present results on the roles of yeast Pol I and Pol III in transcription\, DNA lesion detection and retrotransposon integration. Pol I transcription is regulated through enzyme hibernation (Torreira et al.\, eLife 2017)\, a mechanism that was later shown to operate in other RNA polymerases. Besides\, detection of DNA lesions by Pol I depends on its intrinsic RNA cleavage activity and differs from other RNA polymerases (Sanz-Murillo et al.\, PNAS 2018 ; Santos-Aledo et al.\, Nat Commun 2025). Finally\, Pol III mediates integration of yeast retrotransposon Ty1 upstream of transfer RNA genes\, a mechanism that ensures insertion at safe genome locations (Nguyen et al.\, Nat Commun 2023 ; Huecas et al.\, unpublished). Altogether\, these results underscore the prominent role of RNA polymerases in chromatin-associated cellular processes. \nContact : ibs.seminaires@ibs.fr \n 
URL:https://sfp-alpes.fr/event/carlos-fernandes-tornero-biological-research-center-csic-madrid/
LOCATION:IBS – Salle des séminaires\, IBS 71 avenue des Martyrs\, Grenoble\, 38042\, France
CATEGORIES:Séminaire
ORGANIZER;CN="IBS":MAILTO:ibs.seminaires@ibs.fr
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DTSTART;TZID=Europe/Paris:20261127T140000
DTEND;TZID=Europe/Paris:20261127T160000
DTSTAMP:20261015T150904Z
CREATED:20261015T150904Z
LAST-MODIFIED:20261015T150904Z
UID:10000309-1795788000-1795795200@sfp-alpes.fr
SUMMARY:Soutenance de thèse par Alessio D’ACAPITO (CEA-Irig/IBS)
DESCRIPTION:Study of E. Coli cell wall perforation by bacteriophage T5\nRésumé : \nBacteriophages are fascinating nanomachines that are highly specific and remarkably efficient in infecting their bacterial hosts. While the cell envelope perforation mechanisms by myophages\, such as T4 or of podophages\, such as P22 has been well characterized\, less is known about the molecular mechanisms of the infection of siphophages\, such as T5. \nIn this work\, we used an integrative approach combining cryo-electron tomography (cryo-ET)\, subtomogram averaging (STA) and single particle analysis (SPA) to obtain snapshots at successive stages of phage T5 infection\, from early cell recognition to post DNA injection state. We used E. coli minicells as a simplified cellular model and developed a tailored grid preparation protocol to control the timings of infection and focus on specific timepoints. \nFirst\, we solved the structure of T5 L-shaped fibers at 4Å resolution by SPA. Second\, we characterized by SPA the structure of the adsorbed but noninfecting phage at 4°C by describing a new intermediate of the tube anchoring mechanism\, where the tail tube is brought close to the membrane by the bending of the central fiber but the tube is still closed ; we could conclude that the Cterminal part of the tape measure protein (TMP) pb2-C plays a key structural role. \nLastly\, we solved by STA the structure of the infecting phage tip docked on the minicell and of the trans-periplasmic channel that allows the DNA to be translocated into the bacterial cytosol. We propose a model for the channel\, formed of three copies of the TMP. \nBeyond structural biology\, my PhD work was also focused on building tools for the cryo-ET local community. I have developed a tool for “erasing” the membrane signal from sub-volumes extracted with Dynamo as well as a beginner-friendly method for quick tomogram reconstruction from raw data. We made both publicly available on GitHub.​ ​​​​ \n_ \nLes séminaires et soutenances sont ouverts à tous\, notez toutefois que l’accès au campus EPN nécessite un avis de rendez-vous. Merci de remplir ce formulaire  et de l’adresser\, plus de 48h à l’avance\, à ce contact. \n\n\nPensez à vous munir d’une pièce d’identité le jour de votre visite.
URL:https://sfp-alpes.fr/event/soutenance-de-these-par-alessio-dacapito-cea-irig-ibs/
LOCATION:IBS – Salle des séminaires\, IBS 71 avenue des Martyrs\, Grenoble\, 38042\, France
CATEGORIES:Soutenance,Soutenance de Thèse
ORGANIZER;CN="IBS":MAILTO:ibs.seminaires@ibs.fr
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20261127T140000
DTEND;TZID=Europe/Paris:20261127T160000
DTSTAMP:20261104T201910Z
CREATED:20261104T201910Z
LAST-MODIFIED:20261104T201910Z
UID:10000347-1795788000-1795795200@sfp-alpes.fr
SUMMARY:Soutenance de Thèse par Alessio d’ACAPITO (IBS/MEM & MP)
DESCRIPTION:Study of E. coli cell wall perforation by bacteriophage T5 \nRésumé : \nBacteriophages are fascinating nanomachines that are highly specific and remarkably efficient in infecting their bacterial hosts. While the cell envelope perforation mechanisms by myophages\, such as T4 or of podophages\, such as P22 has been well characterized\, less is known about the molecular mechanisms of the infection of siphophages\, such as T5. \nIn this work\, we used an integrative approach combining cryo-electron tomography (cryo-ET)\, subtomogram averaging (STA) and single particle analysis (SPA) to obtain snapshots at successive stages of phage T5 infection\, from early cell recognition to post DNA injection state. We used E. coli  minicells as a simplified cellular model and developed a tailored grid preparation protocol to control the timings of infection and focus on specific timepoints. \nFirst\, we solved the structure of T5 L-shaped fibers at 4Å resolution by SPA. Second\, we characterized by SPA the structure of the adsorbed but noninfecting phage at 4°C by describing a new intermediate of the tube anchoring mechanism\, where the tail tube is brought close to the membrane by the bending of the central fiber but the tube is still closed ; we could conclude that the Cterminal part of the tape measure protein (TMP) pb2-C plays a key structural role. \nLastly\, we solved by STA the structure of the infecting phage tip docked on the minicell and of the trans-periplasmic channel that allows the DNA to be translocated into the bacterial cytosol. We propose a model for the channel\, formed of three copies of the TMP. \nBeyond structural biology\, my PhD work was also focused on building tools for the cryo-ET local community. I have developed a tool for “erasing” the membrane signal from sub-volumes extracted with Dynamo as well as a beginner-friendly method for quick tomogram reconstruction from raw data. We made both publicly available on GitHub (https://github.com/alessiodacapito). \n_ \nContact : ibs.seminaires@ibs.fr
URL:https://sfp-alpes.fr/event/soutenance-de-these-par-alessio-dacapito-ibs-mem-mp/
LOCATION:IBS – Salle des séminaires\, IBS 71 avenue des Martyrs\, Grenoble\, 38042\, France
CATEGORIES:Soutenance,Soutenance de Thèse
ORGANIZER;CN="IBS":MAILTO:ibs.seminaires@ibs.fr
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