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Filliaux, S. B.

Publications and source records attributed to Filliaux, S. B..

2 recordsLinked to original sources
bioRxiv2024

The Interaction of NF-κB Transcription Factor with Centromeric Chromatin

Centromeric chromatin is a subset of chromatin structure and governs chromosome segregation. The centromere is composed of both CENP-A nucleosomes (CENP-Anuc) and H3 nucleosomes (H3nuc) and is enriched with alpha-satellite (-sat) DNA repeats. These CENP-Anuc have a different structure than H3nuc, decreasing the base pairs (bp) of wrapped DNA from 147 bp for H3nuc to 121 bp for CENP-Anuc. All these factors can contribute to centromere function. We investigated the interaction of H3nuc and CENP-Anuc with NF-{kappa}B, a crucial transcription factor in regulating immune response and inflammation. We utilized Atomic Force Microscopy (AFM) to characterize complexes of both types of nucleosomes with NF-{kappa}B. We found that NF-{kappa}B unravels H3nuc, removing more than 20 bp of DNA, and that NF-{kappa}B binds to the nucleosomal core. Similar results were obtained for the truncated variant of NF-{kappa}B comprised only of the Rel Homology domain and missing the transcription activation domain (TAD), suggesting the RelA TAD is not critical in unraveling H3nuc. By contrast, NF-{kappa}B did not bind to or unravel CENP- Anuc. These findings with different affinities for two types of nucleosomes to NF-{kappa}B may have implications for understanding the mechanisms of gene expression in bulk and centromere chromatin.

biophysics↗
bioRxiv2024

Nanoscale Structure, Interactions, and Dynamics of Centromere Nucleosomes

Centromeres are specific segments of chromosomes responsible for the accurate chromosome segregation process. Centromeres are comprised of two types of nucleosomes: canonical nucleosomes containing an octamer of H2A, H2B, H3, and H4 histones, and CENP-A nucleosomes in which H3 is replaced with its analog CENP-A histone. This modification leads to the difference in the nuclear of DNA turns around the histone core, wrapping efficiency. This value is 121 bp of DNA, considerably less than 147 bp found in canonical nucleosomes. We used Atomic Force Microscopy (AFM) to characterize nanoscale features for both types of nucleosomes assembled on the same template, enabling us to evaluate the effect of internucleosomal interaction. We found that CENP-A mononucleosomes have a lower internucleosomal affinity than canonical H3 nucleosomes. We applied time-lapse, high-speed AFM (HS-AFM) to characterize the dynamics of nucleosomes. For both nucleosomes, spontaneous unwrapping of DNA was observed, and this process occurs via a transient state with [~]100 bp DNA wrapped around the core, followed by a rapid dissociation of DNA. The unwrapping process is asymmetric, so when the dissociation starts on one arm, it enlarges the size of the dissociated arm. Additionally, HS-AFM revealed higher stability of CENP-nucleosomes compared with H3 ones, in which dissociation of the histone core occurs prior to the nucleosome dissociation. The histone core of CENP-A nucleosomes remains intact even after the dissociation of DNA.

biophysics↗