Drosophila DNA polymerase delta. Purification and characterization

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• DNA polymerases are crucial enzymes for DNA replication and repair.
• Mammalian DNA polymerase delta is a key enzyme involved in DNA replication.
• Understanding DNA polymerase function in model organisms like Drosophila melanogaster provides insights into fundamental biological processes.

Purpose of the Study:

• To isolate and characterize a DNA polymerase from early Drosophila melanogaster embryos.
• To determine if this enzyme shares properties with mammalian DNA polymerase delta.
• To investigate the enzymatic activities and subunit composition of the purified Drosophila enzyme.

Main Methods:

• Isolation of DNA polymerase using exclusion chromatography and SDS-PAGE.
• Determination of molecular mass and subunit composition.
• Enzyme activity assays, including inhibition studies and immunological tests.
• Assessment of associated exonuclease activity and stimulation by proliferating cell nuclear antigen.

Main Results:

• A DNA polymerase with a molecular mass of 185 kDa (138- and 47-kDa subunits) was purified.
• The enzyme exhibited properties consistent with DNA polymerase delta, including sensitivity to N-ethylmaleimide and aphidicolin.
• No cross-reactivity was observed with antibodies against Drosophila DNA polymerase alpha.
• Associated 3'-->5'-exonuclease activity, indicative of proofreading, was detected.
• Significant stimulation of polymerase activity by mouse proliferating cell nuclear antigen was observed.

Conclusions:

• The isolated Drosophila melanogaster DNA polymerase exhibits characteristics highly similar to mammalian DNA polymerase delta.
• This enzyme possesses proofreading capabilities and is regulated by proliferating cell nuclear antigen.
• The findings contribute to the understanding of DNA replication mechanisms in eukaryotes using Drosophila as a model system.