Nucleosomal structure of two Drosophila melanogaster simple satellites.

Nucleosomes have been fractionated on nondenaturing polyacrylamide gels, and nucleosome subtypes containing the Drosophila melanogaster specific protein D1 and ubiquitinated core histone H2A were identified by solubility in 0.1 M NaCl before nucleoprotein gel electrophoresis. Nucleosomes which contain DNA complementary to the 1.672 density simple satellite (sequence-AATAT-) bind protein D1, as demonstrated by two-dimensional hybridization mapping. This hybridization pattern allows the identification of D1 dinucleosomes, which, like D1 mononucleosomes, are reduced in mobility on the first dimension (nucleoprotein) gel by the addition of D1, an AT sequence-specific DNA-binding protein. The 1.705 density simple satellite (sequence-AAGAG-) is also found in nucleosomes, in a radically different subset from those of the -AATAT- DNA sequence. -AAGAG- nucleosomes do not contain D1 protein, but appear to be enriched in ubiquitinated core histone H2A. One-dimensional hybridization patterns suggest that -AAGAG- nucleosomal DNA is rapidly trimmed to a shorter DNA length than either bulk or -AATAT- nucleosomes.