X-rays Induced Double Strand Breaks: Damage Distribution and Measurement
The nucleus of mammalian cell is an highly organized and complex structure containing a large amount of DNA arranged at least in three order levels including the nucleosome, the 30 um solenoid and the loops, wich form domains attached at their base to the nuclear matrix 1,2. The latter is an insoluble, structural framework that is composed of elements of the pore complex and lamina, nucleolus and an internal network of ribonucleoproteins attached to a fibrous protein mesh, the scaffoild-proteins 3 Two different forms of chromatin exist. The first, the bulk chromatin, may serve to hide the information content of the genome, with histons playing the role of repressors 4, so that the activity of a genomic region is related to alterations both local and extended of the bulk chromatin 5. The second form of chromatin, active or open chromatin, possess an higher sensitivity and site-restricted hypersensitivity to nucleases action 6,7. This fact has been demostrated both in in vitro cel-lular systems 8 and in fetal and adult erythropoietic tissues 9.
KeywordsStrand Break Double Strand Break Nuclear Matrix Single Strand Break Sedimentation Profile
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