A triplex DNA-binding protein from human cells: purification and characterization.

A protein that binds to an oligonucleotide triplex, (dT)34.(dA)34.(dT)34 (TAT triplex), was purified from HeLa cells by a combination of conventional column chromatography and triplex DNA affinity chromatography. The protein has an apparent molecular mass of 55 kDa on sodium dodecyl sulfate/polyacrylamide gels. Although the protein has an affinity for AT duplex and TAT triplex, a higher affinity for TAT triplex was demonstrated by comparing the elution profiles from an AT duplex and a TAT triplex affinity column. The protein has a moderate affinity for poly(dA-dG).poly(dT-dC) and a very low affinity for single-strand (dA)34 or (dT)34 and various sources of duplex DNA including poly(dA-dT).poly(dA-dT). The possible biological function of this triplex DNA-binding protein is discussed.