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Disintegration of Nascent Replication Bubbles during Thymine Starvation Triggers RecA- and RecBCD-dependent Replication Origin Destruction

Year: 2012
Type: article
Abstract: Thymineless death strikes cells unable to synthesize DNA precursor dTTP, with the nature of chromosomal damage still unclear. Thymine starvation stalls replication forks, whereas accumulating evidence indicates the replication origin is also affected. Using a novel DNA labeling technique, here we show that replication slowly continues in thymine-starved cells, but the newly synthesized DNA becomes fragmented and degraded. This degradation apparently releases enough thymine to sustain initiation of new replication bubbles from the chromosomal origin, which destabilizes the origin in a RecA-dependent manner. Marker frequency analysis with gene arrays 1) reveals destruction of the origin-centered chromosomal segment in RecA + cells; 2) confirms origin accumulation in the recA mutants; and 3) identifies the sites around the origin where destruction initiates in the recBCD mutants. We propose that thymineless cells convert persistent single-strand gaps behind replication forks into double-strand breaks, using the released thymine for new initiations, whereas subsequent disintegration of small replication bubbles causes replication origin destruction. Background: Thymine starvation causes irreversible toxicity and chromosomal damage, by unknown mechanisms. Results: Replication in thymine-starved cells leads to preferential fragmentation and degradation of new DNA and culminates in RecA-dependent destruction of replication origins. Conclusion: DNA replicated in thymine-starved cells is unstable, precipitates irreparable damage of the chromosome. Significance: The mechanisms behind this potent way to kill any organism are becoming clearer.
DOI: 10.1074/jbc.m112.359687
Language: English
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1973620094
FWCI: 1.858
Cites: 54
Cited by: 43
Related to: 10