LONG-RANGE ORGANIZATION AND SEQUENCE-DIRECTED CURVATURE OF XENOPUS-LAEVIS SATELLITE-1 DNA

We have investigated the long-range organization and the intrinsic cur vature of satellite 1 DNA, an unusual tandemly-repeated DNA family of Xenopus laevis presenting sequence homologies to SINEs. PFGE was used in combination with frequent-cutter restriction enzymes not likely to cut within satellite 1 DNA and revealed that almost all the repeating units are tandemly organized to form large arrays (200 kb to 2 Mb) tha t are marked by restriction length polymorphism and contain intra-arra y domains of sequence variation. Besides that, we have analysed the se condary structure of satellite 1 DNA by computer modelling. Theoretica l maps of curvature obtained from three independent models of DNA bend ing (the dinucleotide wedge model of Trifonov, the junction model of C rothers and the model of de Santis) showed that satellite 1 DNA is int rinsically curved and these results were confirmed experimentally by p olyacrylamide gel electrophoresis. Moreover, we observed that this ben ding element is highly conserved among all the members of the satellit e 1 DNA family that are accessible to analysis. A potential genetic ro le for satellite 1 DNA based on this unusual structural feature is dis cussed.