Studies on Deoxyribonucleoprotein Structure

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Abstract
The addition of tRNA to chromatin gel (initial insoluble deoxyribonucleoprotein preparation) in the presence of 1 mM MgCl2 or of 40 mM NaCl results in the transfer of the very lysine‐rich histone (F1) and of some nonhistone proteins to the tRNA, whereas all other histones remain in the deoxyribonucleoprotein. This result provides a new general method for the mild removal of histone F1 from the chromatin gel. The addition of tRNA to chromatin gel in the absence of Mg2+ and Na+ results not only in the rapid removal of histone F1 and of some nonhistone proteins from the chromatin gel, but also in the slow transfer of histones F2a2 and F2b to the tRNA. A similar pattern of histone redistribution is observed when the tRNA (or DNA) is added to the soluble deoxyribonucleoprotein preparation obtained by mechanical disruption of the chromatin gel. There is no protein redistribution in the above‐mentioned soluble deoxyribonucleoprotein preparation (in the absence of exogeneous free polynucleotides). The addition of free DNA or tRNA to the soluble deoxyribonucleoprotein preparation, obtained by treatment of the chromatin gel with 2 M urea, allows one to remove quantitatively histones F1, F2a2 and F2b from the deoxyribonucleoprotein, leaving the initial distribution of the arginine‐rich histones (F2a1 and F3) on the endogeneous DNA unchanged. The redistribution of proteins (and in particular of histones) occurs in the soluble deoxyribonucleoprotein preparation obtained by urea treatment even in the absence of any exogeneous polynucleotides suggesting that conservation of the initial distribution of proteins in this soluble deoxyribonucleoprotein preparation is not complete.

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