[Relationship between transcription and repair of radioinduced DNA damage]

Abstract

The DNA repair is occurred on genome level with different rates. This rates are depend on a transcription activity of various genome sequences. The repair rates are low in non-transcribed genes and DNA sequences, more higher in transcribed genes and the highest in actively transcribed strands of active genes. Such classification could be applied to the repair of UV-induced cyclobutane pyrimidine dimers and for other (but not for all) DNA lesions. This observation has become a basement of such important findings as involvement of transcription into repair or existence of transcription-coupling repair factors (i.e. TFIIH). Thymine glycoles which are appear under ionizing radiation exposure, are repaired preferentially in transcribed DNA. In present reviewer we observe the preferential repair of ionizing radiation-induced single strand breaks (SSBs) in transcribed DNA of human cells. Discontinuous distribution of DNA repair along hole genome has a grate role in biological processes. The data, obtained on cells from patient with rare hereditary disease Cockayne syndrome have shown that there is the defect of preferential repair of pyrimidine dimers and ionizing radiation-induced thymine glycols and SSBs in transcriptionally active DNA sequences. In case of another rare hereditary disease-ataxia telangiectasia the defect of preferential repair of ionizing radiation-indiced SSBs was observed. The defect of preferential repair of radio-induced damages in AT and CS cells can explain such fishers of this diseases as high sensitivity to ionizing radiation.