ANKLE1 is a structure-selective DNA endonuclease that specifically cleaves branched DNA substrates 12. The protein contains both a LEM domain and a GIY-YIG nuclease domain, with the LEM motif binding chr19 via barrier-to-autointegration factor (BAF) 1. Unlike most LEM proteins, ANKLE1 shuttles between nucleus and cytoplasm through canonical nuclear import and export signals 3. ANKLE1 localizes to the midbody during cytokinesis via its N-terminal ankyrin repeats and processes chr19 bridges that connect segregating daughter nuclei 4. The enzyme exhibits unique mechanosensitive properties, specifically cleaving supercoiled or mechanically stretched DNA, which allows it to sense DNA tension and respond to mechanical stress on chr19 bridges 5. ANKLE1 prevents catastrophic bridge breakage by both priming TREX1-mediated resolution and directly cleaving bridge DNA 4. This processing prevents micronuclei formation, reduces DNA damage, and blocks activation of immune responses like the cGAS-STING pathway 4. The catalytic mechanism involves general acid-base catalysis using conserved histidine and tyrosine residues with metal ion coordination 6. Clinically, ANKLE1 variants are associated with increased breast and ovarian cancer risk, and the protein plays important roles in maintaining genomic stability 78.