Structure of the heterodimeric core primase.

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Primases are essential DNA-dependent RNA polymerases that synthesize oligonucleotide primers for DNA replication.
• The core primase in archaea and eukaryotes is a heterodimeric enzyme comprising small and large subunits.

Purpose of the Study:

• To determine the three-dimensional structure of the core primase from the archaeon Sulfolobus solfataricus.
• To elucidate the interaction between the small and large subunits of the core primase.
• To gain insight into the mechanism of template DNA binding and RNA primer synthesis.

Main Methods:

• X-ray crystallography was used to determine the structure of the core primase.
• Biochemical analyses were performed to study subunit interactions and enzyme function.
• Structure-based site-directed mutagenesis was employed to investigate catalytic mechanisms.
• Modeling of a DNA-RNA helix was utilized to understand substrate binding.

Main Results:

• The study provides the first 3D structure of the large subunit of the core primase and its interaction with the small subunit.
• Evolutionary conservation of interface residues suggests a conserved subunit association mode in archaeal and eukaryotic primases.
• The orientation of the large subunit indicates it likely does not directly participate in catalysis.
• Insights into DNA template binding and RNA primer synthesis mechanisms were obtained.

Conclusions:

• The determined structure provides a foundational understanding of archaeal core primase architecture and subunit interactions.
• The findings suggest a conserved mechanism for primase function across archaeal and eukaryotic domains.
• This research offers valuable insights into the fundamental processes of DNA replication initiation.