IDENTIFICATION AND CHARACTERIZATION OF A NUCLEASE ACTIVITY SPECIFIC FOR G4 TETRASTRANDED DNA

We have identified a nuclease activity that is specific for G4 tetrast randed DNA. This activity, found in a partially purified fraction for a yeast telomere-binding protein, binds to DNA molecules with G4 tetra stranded structure, regardless of their nucleotide sequences, and clea ves the DNA in a neighboring single-stranded region 5' to the G4 struc ture. Competition with various G4-DNA molecules inhibits the cleavage reaction, suggesting that this nuclease activity is specific for G4 te trastranded DNA. The existence of this enzymatic activity that reacts with G4 DNAs but not with single-stranded or Watson-Crick duplex DNAs suggests that tetrastranded DNA may have a distinct biological functio n in vivo.