Accumulation of single-strand breaks does not result in double-strand DNA breaks: the peculiarity of transcribing fragment of human ribosomal operon that allows its detection in biological fluids at the death of various cells in organism

摘要

It was shown by blot-hybridization with corresponding DNA-probes after electrophoretic separation of control and experimental samples of human genome DNA that accumulation of single-strand breaks in the chains of double-strand fragment of transcribing range of ribosomal gene (TRrDNA) does not result in double-strand breaks. That differs form the other studied DNA sequences (cluster of histon genes, Alu-repetition, telomeric repetition and satellite III). Single-strand breaks and double-strand breaks were induced by endonucleases and by #gamma#-radiation. In spite of higher chemical modification of TRrDNA by arylazide and dimethylsulfat (because of high content of GC-pairs), under the following fragmentation TRrDNA was found to be more resistant to double-strand breaks than other studied DNA sequences. At the same time in the range of non-transcribing spacer (NTS) of ribosomal gene, the section with higher sensitivity to double-strand breaks was found. Higher resisitance of TRrDNA to double breaks makes it possible to identify these fragments in cell material from different tissue after death or in DNA samples after prolonged storage. Resistance of TRrDNA to formation of double-strand breaks can be used for its detection in biological fluids after cell death, including the death initiated by ionizing radiation.