Suppression of nuclear oscillations in Saccharomyces cerevisiae expressing Glu tubulin

Abstract

In most eukaryotic cells, the C-terminal amino acid of ␣-tubulin is aromatic (Tyr in mammals and Phe in Saccharomyces cerevisiae) and is preceded by two glutamate residues. In mammals, the C-terminal Tyr of ␣-tubulin is subject to cyclic removal from the peptide chain by a carboxypeptidase and readdition to the chain by a tubulin-Tyr ligase. There is evidence that tubulin-Tyr ligase suppression and the resulting accumulation of detyrosinated (Glu) tubulin favor tumor growth, both in animal models and in human cancers. However, the molecular basis for this apparent stimulatory effect of Glu tubulin accumulation on tumor progression is unknown. Here we have developed S. cerevisiae strains expressing only Glu tubulin and used them as a model to assess the consequences of Glu tubulin accumulation in cells. We find that Glu tubulin strains show defects in nuclear oscillations. These defects are linked to a markedly decreased association of the yeast ortholog of CLIP170, Bik1p, with microtubule plus-ends. These results indicate that the accumulation of Glu tubulin in cells affects microtubule tip complexes that are important for microtubule interactions with the cell cortex.

CAP-Gly proteins contribute to microtubule-dependent trafficking via interactions with the C-terminal aromatic residue of α-tubulin

“…Indeed, Nip100 interacts with Snx4, Imh1, Tlg1, Vps20, and Vps60, which are known to be involved in trafficking between endosomes and late Golgi or late Golgi and the vacuole. Notably, and in striking contrast to Bik1 and Nip100, the Cend-tracking protein Bim1, the yeast EB1 ortholog, which is insensitive to the tyrosination status of microtubules, 22,23,32 has not been reported to interact with endosomal proteins. In line with this difference in interaction partners, BIM1 deletion caused no alterations to Snc1 distribution.…”

“…21 Tyrosinated tubulin-dependent effectors were first identified in studies using a Saccharomyces cerevisiae strain exclusively expressing an a-tubulin lacking its terminal aromatic residue (tub1-Glu strain) to model detyrosinated, Glu-tubulin. 22 This work established that Bik1, the yeast ortholog of the mammalian microtubule-associated protein CLIP-170, is sensitive to the tyrosination status of the a-tubulin at microtubule Cends and that it is present in lower amounts at the microtubule extremity in Glu-microtubules. 22 This property was later shown to be shared by the mammalian ortholog, CLIP170, and other proteins containing a CAP-Gly domain, such as p150Glued.…”

“…22 This work established that Bik1, the yeast ortholog of the mammalian microtubule-associated protein CLIP-170, is sensitive to the tyrosination status of the a-tubulin at microtubule Cends and that it is present in lower amounts at the microtubule extremity in Glu-microtubules. 22 This property was later shown to be shared by the mammalian ortholog, CLIP170, and other proteins containing a CAP-Gly domain, such as p150Glued. 23 The CAP-Gly proteins, CLIP170 and p150Glued, are members of the microtubule Cendtracking protein family (known as CTips).…”

Microtubule composition: Cryptography of dynamic polymers

“…In the course of nuclear migration, the nucleus traverses the cell and may oscillate between the mother and daughter cell before cell division. These oscillations are severely dampened in cells expressing Glu tubulin (1). Additional features of spindle dynamics, including the velocity and amplitude of spindle movement ( m͞min) were decreased Ͼ2-fold in cells expressing Glu tubulin.…”

“…Detyrosinated Tubulin (Glu Tubulin) Badin-Larçon et al (1) introduced the truncated version of ␣-tubulin (lacking the terminal phenylalanine, thus exposing glutamate; Glu tubulin) into the yeast genome in place of endogenous TUB1. Yeast microtubules comprised of this truncated form of ␣-tubulin (Glu tubulin), and wild-type ␤-tubulin were able to support cell growth.…”