Evidence is provided that the nucleotide triplet con-sensus non-T(A/T)G (abbreviated to VWG) influences nucleosome positioning and nucleosome alignment into regular arrays. This triplet consensus has been recently found to exhibit a fairly strong 10 bp periodicity in human DNA, implicating it in anisotropic DNA bendability. It is demonstrated that the experimentally determined preferences for nucleosome positioning in native SV40 chromatin can, to a large extent, be pre-dicted simply by counting the occurrences of the period-10 VWG consensus. Nucleosomes tend to form in regions of the SV40 genome that contain high counts of period-10 VWG and/or avoid regions with low counts. In contrast, periodic occurrences of the dinucleotides AA/TT, implicated in the rotational positioning of DNA in nucleosomes, did not correlate with the preferred nucleosome locations in SV40 chromatin. Periodic occurrences of AA did correlate with preferred nucleosome locations in a region of SV40 DNA where VWG occurrences are low. Regular oscillations in period-10 VWG counts with a dinucleosome period were found in vertebrate DNA regions that aligned nucleosomes into regular arrays in vitro in the presence of linker histone. Escherichia coli and plasmid DNA, which fail to align nucleosomes in vitro, lacked these regular VWG oscillations.
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