Characterization of the intramolecular G-quadruplex promoting activity of Est1

► Est1 promotes ssDNA containing four GGG-tracts to form intramolecular G-quadruplex in vitro. ► Mutation at the EF-hand motif of Est1 leads to reduced G-quadruplex promoting activity. ► ssDNA concentration affects Est1's inter- and intramolecular G-quadruplex promoting activity. ► Est1 cannot promote ssDNA lacking four GGG-tracts to form the intramolecular G-quadruplex.