Mouse PrimPol Outperforms Its Human Counterpart as a Robust DNA Primase

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• DNA replication stress poses a significant challenge to genome stability.
• Human PrimPol (Primase-Polymearse) is a key enzyme involved in counteracting replication stress.
• Understanding variations in PrimPol function across species can reveal insights into DNA repair mechanisms.

Purpose of the Study:

• To compare the primase and polymerase activities of Mus musculus PrimPol (MmPrimPol) with its human ortholog.
• To elucidate the structural and functional basis for differences in enzymatic activity between MmPrimPol and human PrimPol.

Main Methods:

• Comparative enzymatic assays measuring primase and DNA polymerase activity.
• Bioinformatic analysis of amino acid sequences and domain structures.
• Structural modeling to infer conformational differences.

Main Results:

• MmPrimPol exhibits significantly higher primase activity compared to human PrimPol.
• MmPrimPol demonstrates enhanced binding to the 5' nucleotide site, facilitating primer initiation.
• A shorter linker in MmPrimPol between the AEP core and Zn finger domain (ZnFD) promotes a primase-ready conformation, but limits DNA polymerization on existing primers.

Conclusions:

• The structural differences, particularly the ZnFD linker length, confer distinct functional properties to MmPrimPol.
• MmPrimPol's robust primase activity is optimized for initiating DNA synthesis under stress, while its polymerase activity is limited.
• These findings highlight species-specific adaptations in DNA replication and repair machinery.