RECOMBINATION HOTSPOT ACTIVITY OF HYPERVARIABLE MINISATELLITE DNA REQUIRES MINISATELLITE DNA-BINDING PROTEINS

Hypervariable minisatellite DNA repents are found at tens of thousands of loci in the mammalian genome. These sequences stimulate homologous recombination in mammalian cells [Cell 60:95-103]. To test the hypoth esis that protein-DNA interaction is required for hotspot function in vivo, we determined whether a second protein binding nearby could abol ish hotspot activity, Intermolecular recombination between pairs of pl asmid substrates was measured in the presence or absence of the cis-ac ting recombination hotspot and in the presence or absence of the secon d trans-acting DNA binding protein. Minisatellite DNA had hotspot acti vity in two cell lines, but lacked hotspot activity in two closely rel ated cell lines expressing a site-specific helicase that bound to DNA adjacent to the hotspot, Suppression of hotspot function occurred for both replicating and non-replicating recombination substrates. These r esults indicate that hotspot activity in vivo requires site occupancy by minisatellite DNA binding proteins.