DIE FUNKTION DER HISTONE

At the present time it is only possible to make assumptions as to the complete biological function, the role and the mode of action of the histones. Their appearance in evolution in stages in which the multicellular organization and the intracellular compartmentalization occurred by means of membranes points to their significance for the life of higher animals, including man. It is possible to demonstrate that the binding of histones to DNA, the resulting change in DNA structure and the restriction of the replicative efficiency of DNA (gene activity) belong to the primary functions of these proteins. The spatial relationships between histones and DNA, and also between the histones themselves, and between them and the other non histone proteins are as yet obscure; the exact molecular processes taking place during repression and de repression of the gene activity by histones are therefore not yet known. The histones are probably unspecific regulators of gene repression, i.e. they may inhibit the transcription of any exposed DNA region which is not occupied by other macromolecules through RNA polymerase. This generalisation of the repressor function of the histones is due to their lack of tissue or species specificity, their low turnover rate, their lack of heterogeneity as well as their even distribution in all regions of the genome of a cell, both active, and inactive ones. In any case, these proteins are important factors in the restriction of genes.