Extreme dNTP pool changes and hypermutability in dcd ndk strains

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Deoxycytidine deaminase (DCD) deficiency causes dNTP pool imbalances, impacting mutagenesis and cellular sensitivity.
• Existing research indicates elevated dCTP and reduced dTTP pools in DCD-deficient cells.

Purpose of the Study:

• To investigate the combined effects of DCD and NDK deficiencies on dNTP pools and mutation rates in Escherichia coli.
• To explore the impact of exogenous nucleosides on replication errors in specific mutant strains.

Main Methods:

• Construction and analysis of double mutants lacking both DCD and NDK in E. coli.
• Quantification of deoxyribonucleotide triphosphate (dNTP) pools.
• Assessment of mutation levels and the effect of thymidine supplementation.
• Investigation of exogenous nucleoside effects on mismatch repair-deficient strains.

Main Results:

• Double DCD/NDK mutants exhibit more extreme dNTP imbalances than single mutants, with dCTP levels significantly exceeding ATP.
• These extreme imbalances result in exceptionally high mutation rates.
• Thymidine supplementation attenuates the high mutation levels observed in DCD/NDK mutants.
• Exogenous nucleosides influence replication errors in DCD-proficient, mismatch repair-deficient strains.

Conclusions:

• Controlling deoxyribonucleotide precursor levels is critical for maintaining genome stability.
• Combined DCD and NDK deficiencies severely disrupt dNTP homeostasis, leading to genomic instability.
• Exogenous nucleosides can modulate replication fidelity, particularly in strains with compromised DNA repair mechanisms.