Detection of satellite DNA in Palorus ratzeburgii: analysis of curvature profiles and comparison with Tenebrio molitor satellite DNA.

Very abundant and homogenous satellite DNA has been found in the flour beetle Palorus ratzeburgii, representing 40% of its genome. Sequencing of 14 randomly cloned satellite monomers revealed a conserved monomer length of 142 bp and an average A+T content of 68%. Sequence variation analysis showed that base substitutions, appearing with a frequency of 2.3%, are predominant differences among satellite monomers. The satellite sequence is unique without significant direct repeats and with only two potentially stable inverted repeats. After electrophoresis of satellite monomers on native polyacrylamide gel retarded mobilities characteristic for curved DNA molecules are observed. The curvature profiles and DNA helix axis trajectory are calculated on the basis of three different algorithms. These calculations predict that P ratzeburgii satellite DNA forms a left-handed solenoid superstructure. Comparison of described features with other satellite DNAs reveals some striking similarities with satellite DNA from related species Tenebrio molitor, which belongs to the same family of Tenebrionidae. Both satellites are very abundant and homogenous with the same, highly conserved monomer length, although there is no homology at the nucleotide level. Their monomers, as well as multimers, exhibit very similar retarded electrophoretic mobilities. The calculated curvature profiles predict two bend centers in monomers of each satellite, resulting in a model of left-handed solenoid superstructures of similar appearance.