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CHROMATIN STATES REESTABLISHMENT AFTER GENOME REPLICATION AND CELL DIVISION

Mardi 12 mars 11:00 - Duree : 1 heure
Lieu : Salle de Conférence de l’IAB - Rond Point de La Chantourne, 38700 La Tronche (arrêt de tram Grand Sablon, ligne B)

Orateur : Marta RADMAN-LIVAJA (IGMM, Montpellier)

I will present results from two projects :

1. RNApol2 and new histone occupancy dynamics on newly replicated DNA.

2. Segregation of Chromatin proteins during asymmetric cell division

In the first part I will describe our findings on RNApol2 and new nucleosome binding to newly-replicated daughter genomes in S. Cerevisiae using our method for following chromatin structure dynamics during replication – ChIP – NChAP – Chromatin Immuno-Precipitation - Nascent Chromatin Avid in Pulldown. The strand specificity of our NGS libraries allowed us to uncover the inherently asymmetric and dynamic distribution of RNApol2 and H3K56ac-a mark of new histones- on daughter chromatids after replication. Our results show a range of distributions on thousands of genes from symmetric to asymmetric with shifts from one strand to the other throughout S-phase. We propose a twostep model of chromatin assembly on nascent DNA which provides a mechanistic framework for the regulation of asymmetric segregation of maternal histones, and discuss our model for chromatin assembly in the context of a mechanism for gene expression buffering without a direct role for H3K56ac.

In the second part I will describe our live-cell imaging approach for recording maternal chromatin segregation patterns during asymmetric yeast cell divisions. Budding yeast undergoes asymmetric divisions producing mother and daughter cells. The mother can generate 20-30 daughters during its replicative lifespan, and most of the factors that determine the phenotypic identity of the mother cell are unknown. We have developed a live cell imaging screen using chromatic proteins fused to the photo-convertible fluorescent protein dendra2 with which we are able to follow the fate of 18 maternal chromatin associated proteins during yeast asymmetric cell divisions. We show that abundant and moderately abundant maternal proteins (estimated at >1300 molecules per cell) segregate stochastically and symmetrically between the mother and the daughter cell with the exception of RXT3 (part of the RPD3L histone deacetylase complex), FPR4 (histone 3 P38 proline isomerase) and TUP1 (transcription repressor), which are retained in the in the mother. Low abundance proteins are preferentially retained in the mother cell with the exception of SIR2 (NAD+ H4K16ac deacetylase, subunit of the heterochromatic Sir complex) and H1 (linker histone), which segregate symmetrically.

Contact : karin.sadoul@univ-grenoble-alpes.fr

Discipline évènement : (Biologie / Chimie)
Entité organisatrice : (IAB)
Nature évènement : (Séminaire)
Evènement répétitif : (Mardis de l’IAB)
Site de l'évènement : Pôle Santé / La Tronche

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