Exo III mapping of the nucleosomes on the 5' Half SNR6 DNA fragments. Chromatin was assembled on the 248 bp DNA fragments labeled at the 5' end of either the top strand (panel A) or the bottom strand (panel B). A 10 bp DNA ladder (Invitrogen) was end-labeled and used as size marker in the lanes M. Sizes of the marker bands are given in the left-hand side of both the panels while arrows on the right-hand side give the sizes of the DNA fragments due to the pauses of Exo III. Lanes 1 and 5 in both the panels show the uncut DNA. Other lanes show naked DNA or chromatin digested for different times by Exo III. (C) Schematic representation of mapping results from the panels A and B. Insert represents the cloned genomic DNA from +62 to +256 bp positions in the SNR6 gene while the flanking 48 and 34 bp are vector-derived DNA. The numbers on right-hand side are the Exo III pauses seen in the gels and represent the nucleosome boundaries.