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

Area of Science:

• Cell Biology
• Structural Biology
• Developmental Biology

Background:

• SSNA1 (septin-like protein 1) is a fibrillar protein involved in microtubule remodeling.
• Its precise molecular mechanism and structural basis for function remain largely unknown.

Purpose of the Study:

• To determine the cryo-electron microscopy (cryo-EM) structure of C.elegans SSNA-1.
• To elucidate the molecular mechanisms underlying SSNA-1's self-assembly and microtubule interactions.
• To evaluate the role of SSNA-1 in embryonic development and cell division.

Main Methods:

• Cryo-electron microscopy (cryo-EM) for structural determination.
• Biochemical assays to analyze protein self-assembly.
• Genetic analysis in C.elegans to assess the functional impact of SSNA-1.

Main Results:

• The cryo-EM structure of C.elegans SSNA-1 was determined at 4.55-Å resolution.
• SSNA-1 forms an anti-parallel coiled-coil structure, with self-assembly mediated by a triple-stranded helical junction.
• The microtubule-binding site is located within this junction, suggesting self-assembly creates microtubule interaction hubs.
• SSNA-1 deletion significantly reduces embryonic viability and causes multipolar spindles.
• Impairing SSNA-1 self-assembly phenocopies the effects of knockout on embryonic viability.

Conclusions:

• This study provides the first structural insights into SSNA-1 self-assembly and its role in microtubule binding.
• SSNA-1 is essential for regulating cell division and maintaining centriole stability.
• The findings highlight the importance of SSNA-1 self-assembly for its biological functions.