Reverse banding on chromosomes produced by a guanosine-cytosine specific DNA binding antibiotic: olivomycin.

Characteristic reverse fluorescent banding patterns (R bands) on human, bovine, and mouse metaphase chromosomes are produced by treating chromosome preparations directly with olivomycin. With the DNA in solution, the repeating polymer poly[d(G-C)] - poly[d((G-C)] (where G is guanine and C is cytosine) enhanced the fluorescence of olivomycin, while the antibotic fluorescence was not affected by the alternating polynucleotide poly]d(A-T)] - poly[d(A-T)] (where A is adenine and T is thymine). Calf thymus DNA, with an intermediate G-C content of about 40 percent, showed a smaller fluorescence enhancement in the presence of olivomycin as was observed for the synthetic polynucleotide poly[d(G-C)] - poly [d(G-C)]. The closely related antibiotic chromomycin A3 showed the same results as were obtained with olivomycin either in the solution interaction with specific DNA's or with the netaphase chromosome preparations. The production of R bands by these G-C-specific DNA binding antibiotics lends credence to the suggestion that the arrangement of the nucleotide sequences along the chromosome is a primary determinant for the appearance of fluorescent bands.