Inhibition of E. coli RecQ Helicase Activity by Structurally Distinct DNA Lesions: Structure-Function Relationships.

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• DNA helicases are crucial enzymes for DNA metabolism.
• DNA lesions can impede helicase function, impacting genomic stability.
• The relationship between DNA lesion structure and helicase inhibition is not well understood.

Purpose of the Study:

• To investigate how different DNA lesion structures affect the unwinding activity and processivity of E. coli RecQ helicase.
• To correlate structural features of DNA lesions with their impact on helicase kinetics.

Main Methods:

• Utilized E. coli RecQ helicase as a model system.
• Assessed unwinding rate constants (k) and processivities (P) for various conformationally defined DNA lesions.
• Quantified helicase-DNA dissociation rate constants (k).

Main Results:

• Intercalated benzo[a]pyrene-adenine adducts showed the highest unwinding rate constants (k).
• Guanine adducts with minor groove or base-displaced intercalated conformations exhibited 10-20 times smaller k values.
• Non-bulky lesions (T(6-4)T, CPD, Sp) had higher k values but significantly reduced processivity (P < 1.0), indicating inhibited unwinding efficiency.

Conclusions:

• DNA lesion conformation and size significantly influence E. coli RecQ helicase unwinding rates and processivity.
• Bulky, intercalated lesions can reduce unwinding rates, while non-bulky lesions can impair overall unwinding efficiency.
• Correlated decreases in unwinding rate and increases in dissociation rate explain the inhibition by non-bulky lesions.