| Gamma-tubulin belongs to the tubulin family and resides primarily within centrosomes as a core element of the microtubule-organizing center across eukaryotes. It assembles into the gamma-tubulin ring complex (gamma-TuRC), which adopts a ring-shaped template that dictates the 13-protofilament architecture of microtubules by anchoring their minus ends and promoting unidirectional polymerization of alpha-beta tubulin dimers. This nucleation activity extends beyond centrosomes, with gamma-TuRCs associating along microtubule lattices to suppress catastrophes and enhance plus-end stability, independent of further nucleation. Gamma-tubulin further organizes into cytosolic gamma-tubules and nuclear-penetrating gamma-strings that interconnect organelles, mitochondria, endosomes, and chromatin, facilitating structural integrity and positioning, such as Golgi ribbon formation and nuclear envelope assembly around chromatin during mitosis. Phosphorylation by SadB kinases at specific serine residues near its C-terminal nuclear localization signal and helix-loop-helix DNA-binding motif triggers nuclear translocation at the G1-S transition, where it accumulates to silence E2F transcriptional activity, inactivate APC/C-Cdh1, and coordinate centrosome duplication with DNA replication alongside cyclin E-Cdk2 and Orc1. In mitosis, gamma-tubulin recruits to pericentriolar material, interacts with checkpoint proteins like BRCA1, Chk2, ATR, Rad51, and tumor suppressors p53 and C53/Daox, while associating with nucleoli outside fibrillar centers to modulate G2/M checkpoint activation post-DNA damage. These interactions link gamma-tubulin to cell cycle regulation, spindle bipolarity via Rab11-endosomes, chromosomal segregation, and cytokinesis fidelity. Elevated gamma-tubulin expression and altered localization occur in tumors including breast cancer, gliomas, glioblastoma, medulloblastoma, myelomas, and non-small cell carcinoma, correlating with centrosome amplification, lymph node metastasis, poor prognosis, and reciprocal modulation with RB1 to sustain E2F-driven proliferation in RB1-deficient contexts. Mutations in TUBG1, such as Leu387Pro in the DNA-binding domain, associate with brain malformations like lissencephaly and microcephaly. |
Lane 1: Hela, Lane 2: COS-7, Lane 3: Hepa1-6, Lane 4: CHO
