The kinetics of DNA synthesis in the mitotic cycle of mouse corneal epithelial cells was studied after a single γ-irradiation of cells in a dose of 4 Gy at different S-phase points. Normally, corneal epitheliocyte S phase consists of S1 and S2 phases separated by an interval during which no DNA is synthesized. The duration of each phase was lengthened after single irradiation due to reparation of injuries in the cells at the expense of the time normally occupied by g1 period of the mitotic cycle. The first event during reparation is excision of damaged complex from the DNA molecule; this complex consists of labeled daughter fragment and matrix site of DNA chain that was used for the synthesis of the daughter fragment. Presumably, the entire reparation process in the cell consists of two stages: "reparative" synthesis and "additional" synthesis. The reparative synthesis, in turn, includes two stages: de novo synthesis of matrix fragment in the DNA chain at the site of the gap formation and de novo synthesis of the daughter fragment after the synthesis of the new matrix fragment is over.

We proposed a new model of supramolecular DNA structure. Similar to the previously developed by us model of primary DNA structure [11-15], 3D structure of DNA molecule is assembled in accordance to a mathematic rule known as Fibonacci sequence. Unlike primary DNA structure, supramolecular 3D structure is assembled from complex moieties including a regular tetrahedron and a regular octahedron consisting of monomers, elements of the primary DNA structure. The moieties of the supramolecular DNA structure forming fragments of regular spatial lattice are bound via linker (joint) sequences of the DNA chain. The lattice perceives and transmits information signals over a considerable distance without acoustic aberrations. Linker sequences expand conformational space between lattice segments allowing their sliding relative to each other under the action of external forces. In this case, sliding is provided by stretching of the stacked linker sequences.

Kinetics of DNA synthesis in mitotic cycle of mouse corneal epithelial cells after single γ-irradiation (4 Gy) at the end of S period was studied by the method of radioautography. Normally, S period of corneal epithelial cells consists of several stages separated by intervals without DNA synthesis. The estimated mean duration of the first (S(1)) and second (S(2)) phases of S period was 16 and 10 h, respectively, and the interval between them was 7 h. Single irradiation at the end of S period changed the duration of mitotic cycle periods: S(2) phase became 2.2-longer than S(1) phase and the duration of g(1) period decreased, because the time for reparation in irradiated cell increases at the expense of g(1) period. Shortening of g(1) period is a factor promoting the appearance of transformed cells.

No abstract

No abstract