Magnesium-dependent association and folding of oligonucleosomes reconstituted with ubiquitinated H2A

The MgCl2-induced folding of defined 12-mer nucleosomal arrays, in which ub iquitinated histone H2A (uH2A) replaced H2A, was analyzed by quantitative a garose gel electrophoresis and analytical centrifugation, Both types of ana lysis showed that uH2A arrays attained a degree of compaction similar to th at of control. arrays in 2 mM MgCl2. These results indicate that attachment of ubiquitin to H2A has little effect on the ability of nucleosomal arrays to form higher order folded structures in the ionic conditions tested, In contrast, uH2A arrays were found to oligomerize at lower MgCl2 concentratio ns than control nucleosomal arrays, suggesting that histone ubiquitination may play a role in nucleosomal fiber association.