Most of the members of the LEM-domain-containing protein family (where LEM represents lamina-associated polypeptide, emerin, MAN1) are transmembrane proteins that span the inner nuclear membrane and interact with the nuclear lamina. Together with barrier-to-autointegration factor (BAF), these proteins regulate nuclear assembly and chromatin organisation. Here, Roland Foisner (p. 1048) and co-workers characterise a LEM-domain-containing protein, ANKLE1 (for ankyrin repeat and LEM domain-containing protein 1), that has rather different functions. Like other LEM proteins, ANKLE1, binds to BAF through the LEM domain. However, ANKLE1 does not reside in the inner nuclear membrane, but instead shuttles between the cytoplasm and the nucleus and has a primarily cytoplasmic localisation at steady state. In addition to the LEM domain, ANKLE1 contains an active GIY-YIG-type endonuclease domain, and the nuclear accumulation of ANKLE1 leads to the formation of DNA double-strand breaks and the induction of a DNA damage response. In addition, ANKLE1 is predominantly expressed in cells of the haematopoietic lineage, which leads the authors to hypothesise that it has a role in mediating genomic rearrangements or DNA repair processes during lymphocyte development.