A model for histone-nonhistone control of ontogenesis.
The co-operation of histones and nonhistones in the known models can sufficiently explain the control of processes occurring within the differentiated cells. To give an explanation--on the same basis--for changes during ontogenesis and for manifestation of the development's program, a new model is needed which supposes the existence of a programming as well as a realizing system. At the start, the realizing system becomes repressed by histones. After this, the programming system gives orders for the production of nonhistones. These latter then activate the adequate (definite) operator of the realizing system and direct, simultaneously, a further programming gene for the production of a specific nonhistone needed for the following step of the program. Further on, the model could give an explanation for the manner in which the differentiated features of the cell are conserved during mitosis. One may suppose, in this case, that the new DNA strands become without delay wholly repressed. The phase-specific nonhistones--characterizing the cell's ontogenesis and produced by direction of the programming genes--will then displace the histones from the adequate DNA-sites.
D006657:Histones; D008954:Models, Biological
D006657:Histones