Figure 2

Archaeal nucleosomes assembled in vivo contain offset helical repeats of AA/AT/TA/TT and CC/GG/GC/CG dinucleotides and lack oligo A/T-rich sequences. The frequencies of occurrence of AA/AT/TA/TT (red line) and CC/GG/GC/CG (blue line) dinucleotides, at each position relative to the center of archaeal nucleosomes assembled (a) in M. thermautotrophicus and (b) in T. kodakarensis (c and d). The ratios of the presence and absence of all pentamers in the DNA molecules protected from MN digestion by nucleosome assembly in M. thermoautotrophicus and in T. kodakarensis, respectively. The graphs show the ratio of occurrence of each of the 1024 possible pentamers in nucleosomal DNA (P_nucleosome) versus in non-nucleosomal DNA (P). As examples, the specific locations on the curves of representative G and/or C only, and A and/or T only pentamers are indicated. As noted, all 32 G and/or C-only pentamers were located preferentially within nucleosomal DNA (blue shaded region), whereas all 32 A and/or T-only pentamers were preferentially excluded from nucleosome incorporation (red shaded region).