DNA nanotubes are widely used as a mimic for cytoskele­tal filaments in bottom-up synthetic biology. Using a synthetic starPEG construct that acts as a crosslinker, we succeed in bundling the few nanome­ter thick DNA nanotubes. In bulk they self assem­ble into micron-scale rings. We achieve their contrac­tion upon temper­a­ture increase or molec­u­lar deple­tion with crowing molecules such as dextran (in collab­o­ra­tion with Kierfeld group, TU Dortmund).

Contrac­tile rings formed from cytoskele­tal filaments mediate the division of cells. Ring forma­tion is induced by specific crosslink­ers for filament bundling forma­tion is induced by specific crosslink­ers, while contrac­tion is typically associ­ated with motor protein activ­ity. Here, we engineer DNA nanotubes as mimics of cytoskele­tal filaments and a synthetic crosslinker based on a peptide-function­al­ized starPEG construct.

The crosslinker induces the bundling of tens of individ­ual DNA nanotubes. Impor­tantly, the DNA nanotube bundles curve into closed micron-scale rings in a one-pot self-assem­bly process yield­ing several thousand rings per micro­liter. Coarse-grained molec­u­lar dynam­ics simula­tions repro­duce detailed archi­tec­tural proper­ties of DNA rings as observed by electron microscopy. Further­more, the simula­tions predict DNA ring contrac­tion – without motor proteins – upon increas­ing DNA nanotube attrac­tion or decreas­ing DNA nanotube bending rigid­ity, yield­ing mecha­nis­tic insights within the parame­ter space relevant for efficient nanotube sliding. We exper­i­men­tally realize these two condi­tions by addition of molec­u­lar crowders or temper­a­ture increase, respec­tively. We obtain ring contrac­tion to less than half of the initial ring diame­ter. These DNA based contrac­tile rings could be a future element of an artifi­cial division machin­ery in synthetic cells. The combi­na­tion of DNA nanotech­nol­ogy and peptide engineer­ing may yield new contrac­tile and muscle-like material.