%0 Journal Article
%T ¦Ã-Tubulin 2 Nucleates Microtubules and Is Downregulated in Mouse Early Embryogenesis
%A Stanislav Vinopal
%A Mark¨¦ta £¿ernohorsk¨¢
%A Vadym Sulimenko
%A Tetyana Sulimenko
%A V¨§ra Voseck¨¢
%A Maty¨¢£¿ Flemr
%A Eduarda Dr¨¢berov¨¢
%A Pavel Dr¨¢ber
%J PLOS ONE
%D 2012
%I Public Library of Science (PLoS)
%R 10.1371/journal.pone.0029919
%X ¦Ã-Tubulin is the key protein for microtubule nucleation. Duplication of the ¦Ã-tubulin gene occurred several times during evolution, and in mammals ¦Ã-tubulin genes encode proteins which share ~97% sequence identity. Previous analysis of Tubg1 and Tubg2 knock-out mice has suggested that ¦Ã-tubulins are not functionally equivalent. Tubg1 knock-out mice died at the blastocyst stage, whereas Tubg2 knock-out mice developed normally and were fertile. It was proposed that ¦Ã-tubulin 1 represents ubiquitous ¦Ã-tubulin, while ¦Ã-tubulin 2 may have some specific functions and cannot substitute for ¦Ã-tubulin 1 deficiency in blastocysts. The molecular basis of the suggested functional difference between ¦Ã-tubulins remains unknown. Here we show that exogenous ¦Ã-tubulin 2 is targeted to centrosomes and interacts with ¦Ã-tubulin complex proteins 2 and 4. Depletion of ¦Ã-tubulin 1 by RNAi in U2OS cells causes impaired microtubule nucleation and metaphase arrest. Wild-type phenotype in ¦Ã-tubulin 1-depleted cells is restored by expression of exogenous mouse or human ¦Ã-tubulin 2. Further, we show at both mRNA and protein levels using RT-qPCR and 2D-PAGE, respectively, that in contrast to Tubg1, the Tubg2 expression is dramatically reduced in mouse blastocysts. This indicates that ¦Ã-tubulin 2 cannot rescue ¦Ã-tubulin 1 deficiency in knock-out blastocysts, owing to its very low amount. The combined data suggest that ¦Ã-tubulin 2 is able to nucleate microtubules and substitute for ¦Ã-tubulin 1. We propose that mammalian ¦Ã-tubulins are functionally redundant with respect to the nucleation activity.
%U http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0029919