Nucleosome chains, folding

The missing internucleosome attraction, however, led to problems when longer nucleosome chains were simulated. Starting from an extended zig-zag conformation, folding of a 25-nucleosome chain occurred within 200 ps and the diameter of the resulting fiber-like structure was 45 nm in approximate agreement with values measured for chicken erythrocyte chromatin. On the other hand, the structure... 

Yoshikawa, Y., Emi, N., Kanbe, T., Yoshikawa, K. and Saito, H. (1996d) Folding and aggregation of DNA chains induced by complexation with lipospermine formation of a nucleosome-like structure and network assembly. FEBSLett., 396, 71-76. 

The ability of the histone-like TAFs to form an octamer-like structure raises the possibility that the TAF octamer may wrap promoter DNA in a manner similar to the nucleosome (Hoffmann et al., 1997 Oelgeschlager et al., 1996). This hypothesis is supported by the resemblance of DNase I footprinting patterns of TFIID on the Adenovirus Major Late (AdML) promoter to those of nucleosomal DNA. However, the arginine side chains in histones that form primary contacts with DNA are not conserved in TAFs (Luger et al., 1997). Therefore, the histone fold domain interaction may be used only for the formation of a compact structure and is not necessarily involved in DNA wrapping. 

Postsynthetic modifications of histones, i.e., phosphorylation, acetylation, and poly(ADP-ribosylation), have been suggested to be involved in the modulation of the structure and the function of chromatin [7, 8]. A central role has been attributed to histone HI in forming and stabilizing the nucleosomal structure and the higher order folding of the polynucleosomal chain into a solenoid conformation [8-10]. 

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