The beta clamp targets DNA polymerase IV to DNA and strongly increases its processivity

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Translesion synthesis (TLS) is a DNA repair mechanism involving specialized DNA polymerases.
• The dinB gene product, Pol IV, is implicated in mutagenesis in Escherichia coli.
• The beta subunit of DNA Pol III is a processivity factor that enhances DNA polymerase activity.

Purpose of the Study:

• To investigate the effect of the beta subunit on the activity and processivity of native DNA Pol IV.
• To determine if the beta subunit influences the interaction of Pol IV with DNA.

Main Methods:

• Biochemical assays were used to study the interaction between Pol IV and the beta subunit.
• DNA binding and complex formation were analyzed in the presence and absence of the beta subunit.
• Processivity of Pol IV was measured with and without the beta subunit.

Main Results:

• In the absence of the beta subunit, Pol IV is distributive and does not form stable DNA complexes.
• The beta subunit allows Pol IV to form a stable initiation complex with DNA.
• The beta subunit dramatically increases Pol IV processivity to 300-400 nucleotides.

Conclusions:

• The beta subunit significantly enhances the biochemical activity of DNA Pol IV.
• The beta subunit may target Pol IV to its DNA substrate in vivo.
• This interaction leads to longer DNA synthesis tracks than previously understood, impacting mutagenesis.