A Southern analysis of nucleosome spacing on CRM1 , CRM2 and CentC. Southern blots of micrococcal nuclease (MNase) digested CRM1, CRM2 and CentC nucleosome cores. (A) Total chromatin was lightly digested with MNase and isolated DNA fragments corresponding to nucleosome monomers, dimers and higher order polymers were separated by gel electrophoresis and probed for CentC and for CRM1 and CRM2 LTRs. (B) A rare fragment, ~30-bp shorter than the majority of the nucleosome dimers, was often visible, especially for CentC (blue arrow). In some cases a shorter fragment could also be seen in the trimer range.