Structural insights into SSNA1 self-assembly and its microtubule binding for centriole maintenance

Area of Science:

• Molecular Biology
• Structural Biology
• Developmental Biology

Background:

• SSNA-1 is a fibrillar protein involved in microtubule remodeling at centrosomes.
• Its precise molecular mechanisms in microtubule nucleation, co-polymerization, and branching remain unclear due to limited structural data.

Purpose of the Study:

• To determine the cryo-EM structure of Caenorhabditis elegans SSNA-1.
• To elucidate the molecular mechanisms underlying SSNA-1 self-assembly and its role in microtubule binding and embryonic development.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine the structure of SSNA-1.
• Genetic analysis in C. elegans to evaluate the function of SSNA-1 during embryonic development.

Main Results:

• The cryo-EM structure revealed SSNA-1 forms an anti-parallel coiled-coil, with C-terminal overhangs facilitating triple-stranded helical junction formation.
• The microtubule-binding region is located within this triple-stranded junction, suggesting self-assembly creates hubs for enhanced microtubule interaction.
• SSNA-1 deletion significantly reduced embryonic viability and increased multipolar spindle formation; impaired self-assembly mimicked these effects.

Conclusions:

• The study provides a high-resolution structure of SSNA-1, clarifying its self-assembly mechanism.
• SSNA-1 self-assembly is critical for effective microtubule binding and proper cell division.
• SSNA-1 plays a vital role in regulating centriole stability, embryonic viability, and cell division in C. elegans.