Nuclear localization of γ‐tubulin affects E2F transcriptional activity and S‐phase progression

Abstract

We show that the centrosome- and microtubule-regulating protein γ-tubulin interacts with E2 promoter binding factors (E2Fs) to modulate E2F transcriptional activity and thereby control cell cycle progression. γ-Tubulin contains a C-terminal signal that results in its translocation to the nucleus during late G1 to early S phase. γ-Tubulin mutants showed that the C terminus interacts with the transcription factor E2F1 and that the E2F1–γ-tubulin complex is formed during the G1/S transition, when E2F1 is transcriptionally active. Furthermore, E2F transcriptional activity is altered by reduced expression of γ-tubulin or by complex formation between γ-tubulin and E2F1, E2F2, or E2F3, but not E2F6. In addition, the γ-tubulin C terminus encodes a DNA-binding domain that interacts with E2F-regulated promoters, resulting in γ-tubulin-mediated transient activation of E2Fs. Thus, we report a novel mechanism regulating the activity of E2Fs, which can help explain how these proteins affect cell cycle progression in mammalian cells.—Höög, G., Zarrizi, R., von Stedingk, K., Jonsson, K., Alvarado-Kristensson, M. Nuclear localization of γ-tubulin affects E2F transcriptional activity and S-phase progression.

The GTPase domain of gamma-tubulin is required for normal mitochondrial function and spatial organization

“…Furthermore, the C-terminal region of γ-tubulin contains the DNA-binding domain and stable expression of γ-tubulin 336-451 co-localizes with the mitochondrial meshwork and nuclear compartment 9, 14 . Both the nuclear compartment and the mitochondria contain chromatin and a double membrane, so accordingly, γ-tubulin associates to both compartments.…”

“…Human pEGFP-γ-tubulin 334–449 (γ-tubulin (334–449)), pEGFP- sh-resistant TUBG1 gene, pEGFP-A13-γ-tubulin resist , and γTubulin shRNA were prepared as previously described 4, 11, 14 . pSpCas9(BB)-2A-GFP γTubulin sgRNA, and pcDNA3-sg-resistant TUBG1 gene were prepared as previously reported 8 .…”

Nuclear functions of prefoldin

“…There is monomeric actin in the nucleus, and its contribution to gene transcription has already been reported (reviewed by [73]). The direct involvement of nuclear tubulin in gene transcription has also been described [74]. c-Myc, the best example of a transcription factor regulated by a prefoldin subunit (see above), also binds tubulin, and the region of the c-Myc protein that interacts with tubulin overlaps its PFDN5 interaction domain [75].…”

The Nuclear Localization of γ-Tubulin Is Regulated by SadB-mediated Phosphorylation

“…In the cytosol, γ-tubulin is part of a ring-shaped protein complex called γTuRC (1, 4–7). Recently, a bipartite nuclear localization signal (NLS) 2 that assists translocation of γ-tubulin to the nucleus was identified in the C terminus of this protein (8). In the nucleus, γ-tubulin regulates E2 promoter-binding factor (E2F) transcriptional activity (8–11), ensuring a transient transcription of genes necessary for centrosomal duplication and DNA-replication (8, 9).…”

“…In the present study, we found that there are two pools of γ-tubulin, one cytosolic and the other nuclear. Using mammalian cell lines (8), we demonstrate that only the cytosolic γ-tubulin pool contains the γTuRC components γ-tubulin complex protein 2 (GCP2) and GCP3. Furthermore, in U2OS and NIH3T3 cells, the size of the nuclear γ-tubulin pool varied, depending on the levels of SadB kinases, and our results show that SadB-mediated phosphorylation of Ser 385 in γ-tubulin regulates the localization and function of γ-tubulin.…”