The function of TUBGCP4 (tubulin gamma complex component 4, ENSG00000137822) is as follows. Component of the gamma-tubulin ring complex (gTuRC) which mediates microtubule nucleation (PubMed:38305685, PubMed:38609661, PubMed:39321809). The gTuRC regulates the minus-end nucleation of alpha-beta tubulin heterodimers that grow into microtubule protafilaments, a critical step in centrosome duplication and spindle formation (PubMed:38305685, PubMed:38609661, PubMed:39321809). {ECO:0000269|PubMed:38305685, ECO:0000269|PubMed:38609661, ECO:0000269|PubMed:39321809}.