The molecular basis of lamin- chromatin interactions [ChIP-Seq]

Lamins are the main constituents of the nuclear lamina, a fibrillar layer underlyingthe inner nuclear membrane. The nuclear lamina governs chromatinorganization through lamina-associated domainswithin the densely packed heterochromatin regions. Employing cryo-focused ion beam (cryo-FIB) milling in conjunction withcryo-electron tomography (cryo-ET), we mappedthe concentration of nucleosomesat the lamin-chromatin interface. Depletion of lamin A/C induces nanometer-scale chromatin decompaction, macroscopic-scale alterations in gene expression and chromatin-wide alterations of chromatin properties, revealed by 4f-genome-wide analysis. Cryo-electron microscopy (cryo-EM) structural analysis revealed a specific interaction between nucleosomes and the tail domain of lamin A. A unique motif of lamin A that distinguishes it from other lamin isoforms. These findings illuminatethe dynamic interplay between specific lamins and chromatin, shaping chromatin architecture and epigenetic regulation. To investigate the role of lamin proteins in chromatin organization, we carried out a comprehensive analysis including 4fSAMMY-seq, RNA-seq, and ChIP-seq for H3K9me3 across wildtype (WT), Lmna-/- (LmnaKO), and Lmnb1-/-+Lmnb2-/- (LBDKO) mouse embryonic fibroblasts (MEFs).Additionally we perfomed ChIP-seq for euchromatin-associated H3K27ac and H3K4me3 histone modifications on WT.