The molecular basis of lamin-specific chromatin interactions
In the cell nucleus, chromatin is anchored to the nuclear lamina, a network of lamin filaments and binding proteins that underly the inner nuclear membrane. The nuclear lamina is involved in chromatin organisation through the interaction of lamina-associated domains (LADs) within the densely packed heterochromatin regions. Employing cryo-focused ion beam (cryo-FIB) milling in conjunction with cryo-electron tomography (cryo-ET), we analysed the distribution of nucleosomes at the lamin-chromatin interface. Depletion of lamin A/C reduced the concentration of nucleosomes at the nuclear periphery, suggesting that lamins are directly involved in the interaction with chromatin. Using cryo-electron microscopy (cryo-EM), we then identified the specific binding motif of the lamin A tail domain that interacts with nucleosomes, distinguishing it from the other lamin isoforms. Furthermore, we examined chromatin structure dynamics using a genome-wide analysis that revealed lamin-dependent macroscopic-scale alterations in gene expression and chromatin remodelling. Our findings provide detailed insights into the dynamic and structural interplay between lamin isoforms and chromatin, molecular interactions which are shaping chromatin architecture and epigenetic regulation.