HIGH RESOLUTION NMR STUDIES OF HISTONES AND THEIR INTERACTIONS WITH DNAReport as inadecuate




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Abstract : The chromosomal complex consists of an approximately equal weight of DNA and basic protein histones together with a variable amount of non-histone acidic protein. Lack of tissue or even organism specificity and extreme immutability suggests a broad structural role for histones in processes of gene control and chromosomal condensation rather than a role of high specificity in recognition of DNA base sequence or as a target for repressor-derepressor molecules. The highly irregular distribution of amino acids in the 5 main histone fractions F1, F2B, F2A1, F2A2, F3 has permitted a determination of which sections of the molecules can participate in histone- histone interactions. Addition of salts to histone solutions results for ail except F1 in the formation of secondary structures resulting in specific broadening of resonances from the less basic portions of the polypeptide chain. It is concluded that these are involved in intra and intermolecular structures. An empirically based spectrum simulation technique is used to aid the analysis. In tlie presence of DNA broadening is observed of resonances from the more basic regions of the histones and it is concluded that these are the sites of interaction with DNA. Histones are therefore envisaged as bringing about structural changes in chromatin by virtue of the fact that only certain parts of the polypeptide chain - in most cases the N and C terminal regions bind to DNA whilst the remainder takes part in histone-histone interactions that are susceptible to external influences. Interactions of the very lysine rich histone F1 have been studied in chromatin gel itself by following the changes in the NMR spectrum accompanying the salt-induced release of this protein. Correlation of the spectral changes and other data with the state of the gel has resulted in a model for the mode of action of F1.





Author: E. Bradbury P. Cary C. Crane-Robinson H. Rattle

Source: https://hal.archives-ouvertes.fr/



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