ON-OFF Switching of Long DNA Transcription of transcription through structural changes/transitions of DNA and DNA-protein complexes. Our results are also very interesting from the perspective of native and artiﬁcial proto-cells. The present ﬁndings show that the ON-OFF switching of transcription is possible without regulatory DNA binding proteins and only requires a phospho- lipid membrane and some cellular environmental factors such as Mg2+ and polyamine. The conformational transition of DNA is induced by changes in the concentrations of Mg2+ and spermine under physiological ionic strength conditions, which accompanies the ON-OFF switching of transcriptional activity of DNA. Phase separation on phospholipid membrane to produce a PE domain may act as a trigger for the adsorption of DNA to the membrane and the recovery of transcriptional activity. In bacteria, changes in the lipid composition of the A R T I C L E S cell membrane in relation to the cell cycle have been reported.53,54 Studies of the roles of phospholipid membrane in DNA function would give us novel and fruitful insights into regulation of DNA structure and function in living and artiﬁcial cells. Supporting Information Available: Materials and Methods, additional footnote and ﬁgures, and a movie of λZAPII/actin DNA on the phospholipd membrane surface of the microdroplet. This material is available free of charge via the Internet at http:// pubs.acs.org. JA105154K (53) Dowhan, W.; Mileykovskaya, E.; Bondanov, M. Biochim. Biophys. Acta 2004, 1666, 19–39. (54) Zang, Y.-M.; Rock, C. O. Nat. ReV. Microbiol. 2008, 6, 222–233. J. AM. CHEM. SOC. 9 VOL. 132, NO. 35, 2010 12471