REPEAT UNITS FROM A MAIZE RDNA EXTERNAL SPACER REGION EXHIBIT DNA CURVATURE AND INTERACT WITH HIGH-MOBILITY-GROUP PROTEINS

The 3-kb external spacer from a maize (Zea mays L. cv. A619) nuclear r RNA gene unit which contains nine highly homologous 200-bp repeat elem ents was found to include a region with DNA-curvature properties. The centre of curvature was localized within repeats 5 and 6 using a circu lar permutation assay. A 60-bp-long subfragment of this region was fou nd to interact with nuclear proteins, including high-mobility-group (H MG) proteins, and with the maize HMGa protein synthesized in Escherich ia coli from a recombinant plasmid. The potential influence of the bin ding of the HMG proteins on the conformation of this subfragment was s tudied with a permutation assay based on a bending vector.