Nuclear growth and import can be uncoupled.

What drives nuclear growth? Studying nuclei assembled in egg extract and focusing on importin α/β-mediated nuclear import, we show that, while import is required for nuclear growth, nuclear growth and import can be uncoupled when chromatin structure is manipulated. Nuclei treated with micrococcal nuclease to fragment DNA grew slowly despite exhibiting little to no change in import rates. Nuclei assembled around axolotl chromatin with 20-fold more DNA than grew larger but imported more slowly.

Measurement of Protein Mobility in Reveals a Unique Tolerance to Osmotic Stress and Temperature Dependence of Diffusion.

Protein mobility in the cytoplasm is essential for cellular functions, and slow diffusion may limit the rates of biochemical reactions in the living cell. Here, we determined the apparent lateral diffusion coefficient ( ) of GFP in as a function of osmotic stress, temperature, and media composition. We find that is much less affected by hyperosmotic stress in than under similar conditions in and .