Movement is what sustains life. Organisms need to move to find food, seek shelter and to reproduce. Mobility is also essential inside organisms where cells are continuously dividing and migrating. There is also unceasing movement inside every cell where myriads of molecules are being trafficked, and cellular compartments of all shapes and sizes shifted. What keeps things moving? Years ago, scientists discovered a protein they coined actin. Actin is a small globular protein that has many different roles in eukaryotic cells. One characteristic feature is its capacity to polymerize into microfilaments that stretch from one end of a cell to another to form the cell's cytoskeleton - which speaks for itself. Though the formation of a cell's cytoskeleton is perhaps considered as actin's fundamental role in the cytoplasm, the protein is also involved in many other activities, one of which is mobility. Actin is also present in the nucleus but, until recently, scientists believed that microfilaments did not form there. It turns out that they do: damaged DNA seems to be oriented towards repair centres thanks to actin microfilaments whose growth is prompted by a protein complex known as Arp2/3.
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