Immunoaffinity purification of DNA polymerase delta

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• DNA polymerase delta (pol delta) is a key enzyme in DNA replication and repair.
• Efficient purification of pol delta is essential for biochemical and structural studies.
• Conventional purification methods for pol delta are often laborious and yield limited amounts of the enzyme.

Purpose of the Study:

• To develop a novel and efficient method for the purification of human DNA polymerase delta (pol delta).
• To utilize a specific monoclonal antibody for immunoaffinity chromatography of pol delta.
• To achieve a high yield of homogeneous pol delta enzyme suitable for further characterization.

Main Methods:

• Isolation and characterization of a monoclonal antibody against human pol delta.
• Immobilization of the antibody onto a hydrazide-activated support via periodate oxidation.
• Purification of calf thymus pol delta using immunoaffinity chromatography followed by ssDNA-cellulose chromatography.

Main Results:

• A single-step immunoaffinity chromatography purification yielded approximately 200-fold purification of pol delta.
• Subsequent ssDNA-cellulose chromatography resulted in a homogeneous enzyme preparation.
• The yield of pure pol delta was significantly higher (approx. 15-fold increase) compared to conventional methods, yielding 0.3 mg from 0.75 kg of calf thymus.

Conclusions:

• The developed immunoaffinity chromatography procedure offers a significant advancement for the facile isolation of pol delta from tissues in high yield.
• The isolated pol delta enzyme consists of associated 125 kDa and 50 kDa subunits.
• These subunits remain associated even under denaturing conditions (2.8 M urea) during ultracentrifugation.