The regulation of transcription depends on protein-induced localized modification of the DNA structure (bending). This modification depends on the nature of the proteins recruited for the tasks and the base sequences in the DNA. The bases stacked in the major and minor grooves (‘the rungs’) of the helix may cause four major categories of architectural alterations relative to each other: (1) twist [slight rotation of the rung], (2) roll [slightly lifting the broader side of a rung], (3) tilt [uplifting the rung at one side], and (4) rise [slipping the rungs away from each other]. The elastic properties of the DNA determine how it is wrapped around histones in the nucleosomal structure, the packing of phage DNA into capsids, super-coiling, DNA looping, etc. These changes are reversible and depend on the physical environment of the DNA. nucleosome, supercoiling, DNA looping, triple helix formation, DNA bending; Beylot B, Spassky A 2001 J Biol Chem 276:25243.
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