Enables DNA topoisomerase type I (single strand cut, ATP-independent) activity. Acts upstream of or within DNA replication; DNA topological change; and embryonic cleavage. Located in cytoplasm; nucleus; and perikaryon. Is expressed in brain; cerebral cortex ventricular layer; cortical plate; and telencephalon. Orthologous to human TOP1 (DNA topoisomerase I). [provided by Alliance of Genome Resources, Apr 2022]