Purification and characterization of Stn1p, a single-stranded telomeric DNA binding protein

In Saccharomyces cerevisiae, Stn1p and Ten1p are required for telomere maintenance. These two proteins and another telomeric single-stranded DNA binding protein, Cdc13p, have been proposed to form a complex to control telomere integrity. In this work, we purified the recombinant Stn1p in Escherichia coli and found that the purified protein could specifically interact with single-stranded telomeric DNA in vitro. Co-fractionation of co-overexpressed Stn1p and Ten1p in insect cells revealed their stable association. A Stn1p/Ten1p binary complex was reconstituted with purified recombinant proteins in vitro. These results indicated that Stn1p and Ten1p interact with each other directly, which is important in telomere length regulation and end protection.