γ-tubulin complexes and microtubule organization

Microtubule nucleation requires γ-tubulin, which exists in two main protein complexes: the γ-tubulin small complex, and the γ-tubulin ring complex. During mitosis, these complexes accumulate at the centrosome to support spindle formation. γ-tubulin complexes are also present at non-centrosomal microtubule nucleation sites, both in interphase and in mitosis. In interphase, non-centrosomal nucleation enables the formation of microtubule bundles or networks of branched microtubules. γ-tubulin complexes may be involved not only in microtubule nucleation, but also in regulating microtubule dynamics. Recent findings indicate that the dynamics of microtubule plus-ends are altered, depending on the expression of γ-tubulin complex proteins.