The cell nucleus is a highly organized and dynamic organelle. This dynamic organization is required for essential nuclear processes, such as gene expression and maintenance of genomic integrity. We study how actin operates in the nucleus to regulate nuclear organization and consequently nuclear processes. In the cytoplasm, actin has a well-established role as a component of the cytoskeleton, and plays important roles for example in cell motility and morphology. In the nucleus, actin has been linked to many processes that regulate gene expression, such as transcription factor regulation, RNA polymerase function and chromatin remodeling, as well as to DNA damage response. However, the molecular mechanisms by which actin functions during these key nuclear events are largely unclear.