Neuronal tau induces DNA conformational changes observed by atomic force microscopy

Neuronal tau associates with chromosome scaffold and localizes in the nuclear and the nucleolar organization regions in neuronal and some non-neuronal cells. Observing the interaction of neuronal tau with DNA under AFM shows that tau binds to DNA as a monomer, and tau–DNA complex forms a beads-on-a-string structure when the mass ratio is 1:10 (molar ratio of tau/DNA ∼1:700 bp). A beads-on-a-coil structure, in which tau is as polymers, will appear when the mass ratio is up to 1:5 (molar ratio of tau/DNA ∼1:350 bp). The present observation that neuronal tau bends the DNA double strands indicates that the appearance of the tau–DNA complex is dependent upon the mass (or molar) ratio of tau and DNA.