Microtubular and Nuclear Functions of γ-Tubulin: Are They LINCed?

Jana Chumová,Petr Halada,Pavla Binarová,Lucie Trögelová,Hana Kourová

doi:10.3390/cells8030259

Jana Chumová, Petr Halada + Show 3 more

Open Access

https://doi.org/10.3390/cells8030259

Copy DOI

Abstract

γ-Tubulin is a conserved member of the tubulin superfamily with a function in microtubule nucleation. Proteins of γ-tubulin complexes serve as nucleation templates as well as a majority of other proteins contributing to centrosomal and non-centrosomal nucleation, conserved across eukaryotes. There is a growing amount of evidence of γ-tubulin functions besides microtubule nucleation in transcription, DNA damage response, chromatin remodeling, and on its interactions with tumor suppressors. However, the molecular mechanisms are not well understood. Furthermore, interactions with lamin and SUN proteins of the LINC complex suggest the role of γ-tubulin in the coupling of nuclear organization with cytoskeletons. γ-Tubulin that belongs to the clade of eukaryotic tubulins shows characteristics of both prokaryotic and eukaryotic tubulins. Both human and plant γ-tubulins preserve the ability of prokaryotic tubulins to assemble filaments and higher-order fibrillar networks. γ-Tubulin filaments, with bundling and aggregating capacity, are suggested to perform complex scaffolding and sequestration functions. In this review, we discuss a plethora of γ-tubulin molecular interactions and cellular functions, as well as recent advances in understanding the molecular mechanisms behind them.

Highlights

Introduction γTubulin belongs to the eukaryotic clade of tubulins [1] and both human and plantArabidopsis γ-tubulins show the highest similarity—on the sequence and structural levels—to β-tubulins and bacterial BTubA and BTubB of Prosthecobacter dejongeii [2]
As microtubule nucleation has been widely discussed in comprehensive review articles over the last few years [15,16], we provide a short overview concerning γ-tubulin function in centrosomal and non-centrosomal nucleation pathways and other γ-tubulin roles with cytoskeletons. γ-Tubulin ring complexes built of tetrameric γ-tubulin small complexes and of other specific components serve as templates for microtubule nucleation [17]
Principles of microtubule nucleation either from centrosomes or from non-centrosomal sites are remarkably conserved in eukaryotes

Summary

Functions of γ-Tubulin in the Cell Cycle Regulation and in Nuclear Processes

The microtubule-independent role of γ-tubulin in the cell cycle was reported from different eukaryotes. Lamins and associated proteins localized at the inner surface of the nuclear envelope interact in a dynamic manner with chromatin Their role in the organization of chromatin domains, in transcription, replication, and DNA repair is known (reviewed in Reference [77]). In spite of the fact that microtubule nucleation from the nuclear envelope and from pre-existing spindle microtubules is of high importance in the plant cells where centrosomes are absent, the data on the possible interaction and function of γ-tubulin with LINC/SUN/KASH proteins are not yet available. GIP proteins localize with the outer nuclear envelope, which is a site of acentrosomal microtubule nucleation in plants, and are present in the nuclei beneath the inner nuclear membrane. We can expect that the interaction of γ-tubulin with GIPs and SUN proteins might be functional in connecting the nuclear organization with microtubular dynamics. The contribution of the interaction of the MSL6 protein with γ-tubulin to the mechanosensing in plants is only hypothetical under the current state of knowledge

Concluding Remarks

Co-Purification