Efficient long DNA gap-filling in a mammalian cell-free system: A potential new in vitro DNA replication assay

► Reaction of HeLa cell extract with circular duplex substrates containing a long gap induces efficient DNA synthesis in vitro. ► We constructed a mammalian cell-free system in which radiolabelling is not required, and DNA synthesis is quantifiable. ► In this system, physiological DNA replication, particularly the elongation process, may be reproduced. ► Quantitative assay of mammalian DNA replication may provide various advantages.