Biology subjects

Hamiche, A.

Publications and source records attributed to Hamiche, A..

4 recordsLinked to original sources

bioRxiv2021

Differential Histone-DNA Interactions Dictate Nucleosome Recognition of the Pioneer Transcription Factor Sox

Pioneer transcription factors (PTFs) have the remarkable ability to directly bind to chromatin for stimulating vital cellular processes. In this work, we dissect the universal binding mode of Sox PTF by combining extensive molecular simulations and DNA footprinting techniques. As a result, we show that when Sox consensus DNA is located at the solvent-facing DNA strand, Sox binds to the compact nucleosome without imposing any significant conformational changes. We also reveal that the basespecific Sox:DNA interactions (base reading) and the Sox-induced DNA changes (shape reading) are concurrently required for the sequence-specific DNA recognition. Among different nucleosomal positions, such a specific reading mechanism is satisfied solely at superhelical location 2 (SHL2). While SHL2 acts transparently to Sox binding, SHL4 permits only shape reading, and SHL0 (dyad) allows no reading mechanism. These findings demonstrate for the first time that Sox-based nucleosome recognition is essentially guided by the distinct histone-DNA interactions, permitting varying degrees of DNA flexibility.

biophysics↗

bioRxiv2020

The H2A.J histone variant contributes to Interferon-Stimulated Gene expression in senescence by its weak interaction with H1 and the derepression of repeated DNA sequences

The histone variant H2A.J was previously shown to accumulate in senescent human fibroblasts with persistent DNA damage to promote inflammatory gene expression, but its mechanism of action was unknown. We show that H2A.J accumulation contributes to weakening the association of histone H1 to chromatin and increasing its turnover. Decreased H1 in senescence is correlated with increased expression of some repeated DNA sequences, increased expression of STAT/IRF transcription factors, and transcriptional activation of Interferon-Stimulated Genes (ISGs). The H2A.J-specific Val-11 moderates the transcriptional activity of H2A.J, and H2A.J-specific Ser-123 can be phosphorylated in response to DNA damage with potentiation of its transcriptional activity by the phospho-mimetic S123E mutation. Our work demonstrates the functional importance of H2A.J-specific residues and potential mechanisms for its function in promoting inflammatory gene expression in senescence.

genetics↗

bioRxiv2019

H2A.Z is dispensable for both basal and activated transcription in post-mitotic mouse muscles

The histone variant H2A.Z is enriched in nucleosomes surrounding the transcription start site of active promoters, suggesting that it might be implicated in transcription. It is also required during mitosis. However, evidences obtained so far mainly rely on correlative evidences obtained in actively dividing cells. We have defined a paradigm in which cell cycle cannot interfere with H2A.Z transcriptional studies by developing an in vivo systems to invalidate H2A.Z in terminally differentiated post-mitotic muscle cells to dissociate its role during transcription from its role during mitosis. ChIP-seq, RNA-seq and ATAC-seq experiments performed on H2A.Z KO post-mitotic muscle cells show that this histone variant is neither required to maintain nor to activate transcription. Altogether, this study provides in vivo evidence that in the absence of mitosis H2A.Z is dispensable for transcription and that the enrichment of H2A.Z on active promoters is rather a marker than an actor of transcriptional activity.

cell biology↗

bioRxiv2017

3D clustering analysis of super-resolution microscopy data by 3D Voronoi tessellations

Single-molecule localization microscopy (SMLM) can play an important role in integrated structural biology approaches for example at the interface of cryo electron microscopy (cryo-EM), X-ray crystallography, NMR and fluorescence imaging to identify, localize and determine the 3D structure of cellular structures. While many tools exist for the 3D analysis and visualisation of crystal or cryo-EM structures little exists for 3D SMLM data which can provide fascinating insights but are particularly challenging to analyze in three dimensions especially in a dense cellular context. We developed 3DClusterViSu, a method based on 3D Voronoi tessellations that allows local density estimation, segmentation & quantification of 3D SMLM data and visualization of protein clusters within a 3D tool. We show its robust performance on microtubules and histone proteins H2B and CENP-A with distinct spatial distributions. 3DClusterViSu will favor multi-scale and multi-resolution synergies to allow integrating molecular and cellular levels in the analysis of macromolecular complexes.

bioinformatics↗