Dynamizing nuclear actin filaments.

While it is long known that actin is part of the nuclear proteome, its properties and functions as regulated, functional and dynamically assembled actin filaments are only recently emerging. Thus, newly uncovered roles for intranuclear actin filaments are opening new perspectives on how the nucleus and its genomic content may be organized in particular with regard to a given stage of the cell cycle. Here, we summarize recent studies on actin filament polymerization and turnover within the nuclear compartment of mammalian cells. We emphasize and discuss novel findings, in which transient and dynamic nuclear actin filaments have been visualized in physiological contexts, and focus on aspects of signalling mechanisms, chromatin reorganization and DNA repair. Further, a better understanding of the spatiotemporal control of nuclear actin-regulating factors in mammalian cells will ultimately provide a more detailed view on how the nuclear F-actin cytoskeleton contributes to genome organization and nuclear architecture.