Gold-nanoparticle-assisted laser perturbation of chromatin assembly reveals unusual aspects of nuclear architecture within living cells.

Chromatin organization within the nucleus is a vital regulator of genome function, yet its mechanical coupling to the nuclear architecture has remained elusive. To directly investigate this coupling, we locally modulated chromatin structure in living cells using nanoparticle-based laser perturbation. Unusual differences in the response of the cell nucleus were observed depending on the nuclear region that was perturbed--the heterochromatin, the euchromatin, and the nuclear envelope. This response varied under different conditions of cellular perturbations such as ATP depletion, apoptosis, and inhibition of histone deacetylases. Our studies implicate heterochromatin organization in imparting mechanical stability to the cell nucleus and suggest that nuclear size and shape are the result of interplay between nuclear and cytoplasmic anchors.