A primase subunit essential for efficient primer synthesis by an archaeal eukaryotic-type primase

Area of Science:

• Molecular Biology
• Archaea Biology
• Biochemistry

Background:

• Archaea utilize a eukaryotic-type primase composed of catalytic (PriS) and noncatalytic (PriL) subunits.
• The precise composition and function of archaeal primase complexes are not fully elucidated.

Purpose of the Study:

• To identify and characterize novel components of the archaeal primase complex.
• To investigate the role of these components in DNA replication.

Main Methods:

• Protein identification and characterization in Sulfolobus solfataricus.
• Crystallographic analysis and sequence comparisons.
• Phylogenomic analysis.
• Biochemical assays for nucleotide substrate affinity and primer synthesis activity.

Main Results:

• A new essential primase noncatalytic subunit, PriX, was identified in Sulfolobus solfataricus.
• PriX is a diverged homologue of PriL's C-terminal domain and lacks an iron-sulfur cluster.
• PriX, PriL, and PriS form a stable heterotrimer (PriSLX) with enhanced nucleotide substrate affinity and primer synthesis activity compared to the PriSL heterodimer.
• PriL, but not PriX, facilitates primer extension by PriS.

Conclusions:

• PriX is essential for archaeal survival and plays a crucial role in DNA primer synthesis.
• The formation of the PriSLX complex enhances primase activity.
• The catalytic activity of PriS is modulated by interactions with both PriL and PriX.