Guanine-rich (GGNNGG) elements at chromosomal breakpoints interact with a loop-forming, single-stranded DNA-binding protein.

Proto-oncogene-activation is frequently preceded by chromosomal translocations. Several models suggest that DNA single-strands and loops may serve as intermediates in the process of illegitimate recombination. Guanine-rich, repetitive elements are preferred sites of chromosomal exchange and can undergo conformational changes which result in the generation of single-stranded DNA. Here we describe a single-stranded DNA-binding protein which binds specifically to guanine-rich elements at the breakpoints of human reciprocal translocations, including the t(14;18), t(2;8), t(9;22), t(15;17) and t(4;11) in leukemia and lymphoma. The primitive binding consensus consists of two guanine-residues on either side separated by a spacer of at least two nucleotides (GGN-NGG). Binding activity is unaltered by a spacer length of up to 46 nucleotides. These data suggest that the protein has the unique ability to form or stabilize DNA-loops and may thus play a general role in recombination.