Gamma Radiation as a Probe of Chromatin Structure: Damage to and Repair of Active Chromatin in the Metaphase Chromosome

Cobalt-60 γ radiation has been employed as a means of preferentially damaging actively transcribing chromatin within interphase and metaphase Chinese hamster V79-379 lung fibroblasts. The single-strand size distribution and break frequency of bulk 3 H-labeled DNA have been compared to those same par...

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Bibliographic Details
Published in:Radiation research 1984-06, Vol.98 (3), p.629-641
Main Authors: Oleinick, Nancy L., Chiu, Song-Mao, Friedman, Libby R.
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Cells, Cultured
Chromatin
Chromatin - radiation effects
Chromatin. Chromosome
Chromosomes
Chromosomes - radiation effects
Cricetinae
Cricetulus
DNA
DNA damage
DNA Repair - radiation effects
DNA, Single-Stranded - radiation effects
Fibroblasts - radiation effects
Fibroblasts - ultrastructure
Fundamental and applied biological sciences. Psychology
Gamma Rays
HeLa cells
Interphase
Interphase - radiation effects
Kinetics
Lung - radiation effects
Lung - ultrastructure
Metaphase
Metaphase - radiation effects
Molecular and cellular biology
Molecular genetics
Radiation damage
Radiation Tolerance
RNA
Space life sciences
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Summary:Cobalt-60 γ radiation has been employed as a means of preferentially damaging actively transcribing chromatin within interphase and metaphase Chinese hamster V79-379 lung fibroblasts. The single-strand size distribution and break frequency of bulk 3 H-labeled DNA have been compared to those same parameters for active sequences, i.e., sequences complementary to ^{125}{\rm I}\text{-labeled}\ {\rm poly}({\rm A}+){\rm RNA}$. The results show that (a) sequences active during interphase are more sensitive than inactive sequences to single-strand break formation by γ radiation even when the chromatin is condensed in metaphase, (b) repair of strand breaks in the bulk DNA is slower in metaphase than in interphase cells, but (c) during metaphase, repair is faster in active sequences than in the bulk DNA. Furthermore, this study demonstrates that chromatin structure can be probed within intact cells by a method which circumvents isolation of nuclei or chromatin and the use of exogenous nucleases.
ISSN:0033-7587
1938-5404
DOI:10.2307/3576494