[Factors influencing DNA repair processes of the cell cycle].

DNA repair is an essential mechanism also for cells within the mitotic cycle. Among other things, the modification of chromatin proteins (mainly histones) is one of the premises for this. In this context special importance is attributed to the poly(ADP-ribose) polymerase which is activated at the occurrence of breaks in DNA strands. Poly(ADP-ribosylation) of histones is suggested to be responsible for loosening of the nucleosome core which is an alteration of the histone structure favouring the processes of DNA repair. Poly(ADP-ribosylation) is also involved in the processes of chromatin condensation which may result in cross-linking of H1-histones. This form of ribosylation also seems to be effective in the translocation of the nucleosome core in already repaired DNA strands. Whereas methylation processes are needed for restrictions, acetylation and phosphorylation reactions are presumably necessary for DNA reduplication and DNA transcription.