MAPPING INDIVIDUAL COSMID DNAS BY DIRECT AFM IMAGING

Individual cosmid clones have been restriction mapped by directly imag ing, with the atomic force microscope (AFM), a mutant EcoRI endonuclea se site-specifically bound to DNA, Images and data are presented that locate six restriction sites, predicted from gel electrophoresis, on a 35-kb cosmid isolated from mouse chromosome 7. Measured distances bet ween endonuclease molecules bound to lambda DNA, when compared to know n values, demonstrate the accuracy of AFM mapping to better than Icb. These results may be extended to identify other important site-specifi c protein-DNA interactions, such as transcription factor and mismatch repair enzyme binding, difficult to resolve by current techniques. (C) 1997 Academic Press.