Electron microscopic mapping of wheat germ RNA polymerase II binding sites on cloned CaMV DNA.

The binding sites of wheat germ RNA polymerase II were mapped on the cloned CaMV genome by observation of enzyme-linear DNA complexes by electron microscopy. Twelve sites are observed. Three of them are relatively stable in the presence of heparin and are found at positions 8-9, 21-23, and 41-44 map units on the physical map of the genome. These positions correspond to AT-rich regions of the viral genome which contain potential promoter sites. These results are discussed with reference to current information on the structure and expression of the CaMV genome.