Gamma-tubulin coordinates nuclear envelope assembly around chromatin

Area of Science:

• Cell Biology
• Molecular Biology
• Developmental Biology

Background:

• The role of gamma-tubulin (γ-tubulin) in the cytoplasm as a microtubule organizer is well-established.
• Its function within the cell nucleus remains largely unexplored.

Purpose of the Study:

• To investigate the nuclear function of γ-tubulin in eukaryotic cells.
• To elucidate the mechanism by which γ-tubulin contributes to nuclear formation and organization.

Main Methods:

• Studied γ-tubulin localization in demembranated *Xenopus laevis* sperm chromatin.
• Utilized immunodepletion techniques to assess the impact of γ-tubulin on nuclear assembly.
• Examined γ-tubulin's role in mammalian cell lines during nuclear formation.
• Expressed a γ-tubulin mutant lacking DNA-binding domain to analyze its function.

Main Results:

• γ-tubulin is present throughout *Xenopus laevis* sperm chromatin and recruits nuclear components during nucleus formation.
• γ-tubulin depletion disrupts lamina and nuclear membrane assembly in *X. laevis*.
• In mammalian cells, γ-tubulin establishes a protein boundary around chromatin, coordinating daughter nuclei assembly.
• A mutant γ-tubulin lacking DNA-binding forms aberrant, chromatin-empty nuclear structures, highlighting the importance of chromatin association.

Conclusions:

• A dynamic interplay between cytosolic and chromatin-associated γ-tubulin is essential for proper nuclear formation.
• γ-tubulin forms a nuclear protein meshwork around chromatin, coordinating nuclear assembly in eukaryotic cells.
• Impairment of the γ-tubulin pool balance leads to aberrant nuclei formation.