γ-Tubulin in microtubule nucleation and beyond

Microtubules composed of alpha beta -tubulin dimers are dynamic cytoskeletal polymers that play key roles in essential cellular processes such as cell division, organelle positioning, intracellular transport, and cell migration. gamma -Tubulin is a highly conserved member of the tubulin family that is required for microtubule nucleation. gamma -Tubulin, together with its associated proteins, forms the gamma -tubulin ring complex (gamma -TuRC), that templates microtubules. Here we review recent advances in the structure of gamma -TuRC, its activation, and centrosomal recruitment. This provides new mechanistic insights into the molecular mechanism of microtubule nucleation. Accumulating data suggest that gamma -tubulin also has other, less well understood functions. We discuss emerging evidence that gamma -tubulin can form oligomers and filaments, has specific nuclear functions, and might be involved in centrosomal cross-talk between microtubules and microfilaments.