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Thymine metabolism and thymineless death in prokaryotes and eukaryotes
S I Ahmad1, S H Kirk, A Eisenstark
1Department of Life Sciences, Nottingham Trent University, England. lif3ahmadsi@NTU.AC.UK
Annual Review of Microbiology
|January 19, 1999
Summary
Thymine starvation causes cell death (thymineless death, TLD) in microorganisms, unlike other nutrient deprivations. DNA damage and repair pathways, particularly RecF, are key to this lethal effect.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Thymineless death (TLD) is a unique phenomenon where thymine starvation, unlike deprivation of other nutrients, causes microbial cell death.
- TLD involves direct DNA damage, including single- and double-strand breaks, and indirect effects like plasmid loss and filamentation.
Purpose of the Study:
- To elucidate the molecular mechanisms underlying thymineless death (TLD) in microorganisms.
- To investigate the roles of DNA repair pathways, specifically recombinational repair, in TLD sensitivity and recovery.
Main Methods:
- Analysis of microbial responses to thymine starvation.
- Genetic studies involving mutations in DNA repair genes (recBCD, RecF).
- Comparison of TLD mechanisms in bacteria and yeast.
Main Results:
- Thymine starvation induces both single- and double-strand DNA breaks, with double-strand breaks being lethal.
- Mutations in recBCD increase TLD sensitivity, while RecF pathway mutations enhance recovery, suggesting RecF's critical role.
- Indirect effects include plasmid elimination, altered nucleotide pools, and phage induction.
Conclusions:
- The RecF repair pathway may be crucial for TLD by increasing specific double-strand DNA break configurations.
- Similarities exist between bacterial TLD and eukaryotic cell death, suggesting conserved mechanisms.
- Understanding TLD is vital for developing anticancer drugs and antibiotics targeting thymidylate metabolism.