DNA Motions in the nucleosome core particle: A reanalysis

✍ Scribed by J. Michael Schurr; Rebecca L. Schurr

• Publisher: Wiley (John Wiley & Sons)
• Year: 1985
• Tongue: English
• Weight: 474 KB
• Volume: 24
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360241007

✦ Synopsis

Transient photodichroism (TPD) data of Wang, Hogan and Austin [(1982) Proc. Null. Acud. Sci. USA 79, 5896-59001 for methylene blue intercalated in nucleosomal DNA are reanalyzed using correct expressions for the twisting correlation functions of short DNAs. The data are found to rule out several models, including one in which the helix axis is constrained to girdle the equator of the sphere (representing a core particle) but the DNA is everywhere able to undergo twisting deformations and/or spinning around its local helix axis. However, when the ends of the DNA are rigidly clamped (against twisting/spinning) to the sphere, the same model gives an excellent fit to the data with suitable choices of parameters. From these and other observations, it is concluded that nucleosomal DNA must be rigidly clamped to the core particle at one or more points, although it is free to twist at most sites of binding of the dye. Moreover, if the dye is actually bound between two clamped points, then the torsional rigidity of DNA in the nucleosome is at least 2.5 times smaller than that of an ordinary linear DNA.