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Mzt1/Tam4, a fission yeast MOZART1 homologue, is an essential component of the γ-tubulin complex and directly interacts with GCP3(Alp6).

Dhani DK, Goult BT, George GM, Rogerson DT, Bitton DA, Miller CJ, Schwabe JW, Tanaka K - Mol. Biol. Cell (2013)

Bottom Line: Mzt1/Tam4 depletion also causes cytokinesis defects, suggesting a role of the γ-tubulin complex in the regulation of cytokinesis.Yeast two-hybrid analysis shows that Mzt1/Tam4 forms a complex with Alp6, a fission yeast homologue of γ-tubulin complex protein 3 (GCP3).Together our results suggest that Mzt1/Tam4 contributes to the MTOC function through regulation of GCP3(Alp6).

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Leicester, Leicester LE1 9HN, United Kingdom Paterson Institute for Cancer Research, University of Manchester, Manchester M20 4BX, United Kingdom.

ABSTRACT
In humans, MOZART1 plays an essential role in mitotic spindle formation as a component of the γ-tubulin ring complex. We report that the fission yeast homologue of MOZART1, Mzt1/Tam4, is located at microtubule-organizing centers (MTOCs) and coimmunoprecipitates with γ-tubulin Gtb1 from cell extracts. We show that mzt1/tam4 is an essential gene in fission yeast, encoding a 64-amino acid peptide, depletion of which leads to aberrant microtubule structure, including malformed mitotic spindles and impaired interphase microtubule array. Mzt1/Tam4 depletion also causes cytokinesis defects, suggesting a role of the γ-tubulin complex in the regulation of cytokinesis. Yeast two-hybrid analysis shows that Mzt1/Tam4 forms a complex with Alp6, a fission yeast homologue of γ-tubulin complex protein 3 (GCP3). Biophysical methods demonstrate that there is a direct interaction between recombinant Mzt1/Tam4 and the N-terminal region of GCP3(Alp6). Together our results suggest that Mzt1/Tam4 contributes to the MTOC function through regulation of GCP3(Alp6).

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A speculative model for Mzt1 function to activate γ-TuC. Model adapted from the one proposed by Kollman et al. (2011). A ring-like γ-TuSC made of GCP2, GCP3, and γ-tubulin carries 13 γ-tubulins, which are not evenly distributed. Mzt1 oligomer incorporated into the γ-TuC may be recruited to the bottom of the ring-like structure via its interaction with GCP3. The Mzt1 oligomer stabilizes the whole complex, resulting in the 13 γ-tubulin molecules being more evenly distributed and leading to more efficient MT nucleation.
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Figure 7: A speculative model for Mzt1 function to activate γ-TuC. Model adapted from the one proposed by Kollman et al. (2011). A ring-like γ-TuSC made of GCP2, GCP3, and γ-tubulin carries 13 γ-tubulins, which are not evenly distributed. Mzt1 oligomer incorporated into the γ-TuC may be recruited to the bottom of the ring-like structure via its interaction with GCP3. The Mzt1 oligomer stabilizes the whole complex, resulting in the 13 γ-tubulin molecules being more evenly distributed and leading to more efficient MT nucleation.

Mentions: If Mzt1 acts as the GCP3 modulator to “straighten up” the GCP3, our data suggest that Mzt1 may not be a mere splint. The predicted “hinge” region of GCP3Alp6, residues 499–503 (based on the predicted human GCP3 hinge region, 551–555; Guillet et al., 2011), is distal to the GCP3Alp6 N-terminal region (1–186), which interacts with Mzt1 (Figure 6F and Supplementary Figure S3). The N-terminal end of budding yeast GCP3Spc98 has been mapped to the base of the γ-TuSC (Choy et al., 2009). Considering the fact that purified recombinant Mzt1 forms oligomers, one possibility is that Mzt1 forms a multimer complex that fits deep inside the funnel-shaped γ-tubulin ring-like complex and adjusts the angle of the GCP3 (Figure 7). Narrowing down the Mzt1 interaction region in GCP3Alp6 and performing structural analysis of the Mzt1-Alp6 complex are essential to finding out the precise molecular mechanism by which Mzt1 regulates the γ-TuC.


Mzt1/Tam4, a fission yeast MOZART1 homologue, is an essential component of the γ-tubulin complex and directly interacts with GCP3(Alp6).

Dhani DK, Goult BT, George GM, Rogerson DT, Bitton DA, Miller CJ, Schwabe JW, Tanaka K - Mol. Biol. Cell (2013)

A speculative model for Mzt1 function to activate γ-TuC. Model adapted from the one proposed by Kollman et al. (2011). A ring-like γ-TuSC made of GCP2, GCP3, and γ-tubulin carries 13 γ-tubulins, which are not evenly distributed. Mzt1 oligomer incorporated into the γ-TuC may be recruited to the bottom of the ring-like structure via its interaction with GCP3. The Mzt1 oligomer stabilizes the whole complex, resulting in the 13 γ-tubulin molecules being more evenly distributed and leading to more efficient MT nucleation.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Figure 7: A speculative model for Mzt1 function to activate γ-TuC. Model adapted from the one proposed by Kollman et al. (2011). A ring-like γ-TuSC made of GCP2, GCP3, and γ-tubulin carries 13 γ-tubulins, which are not evenly distributed. Mzt1 oligomer incorporated into the γ-TuC may be recruited to the bottom of the ring-like structure via its interaction with GCP3. The Mzt1 oligomer stabilizes the whole complex, resulting in the 13 γ-tubulin molecules being more evenly distributed and leading to more efficient MT nucleation.
Mentions: If Mzt1 acts as the GCP3 modulator to “straighten up” the GCP3, our data suggest that Mzt1 may not be a mere splint. The predicted “hinge” region of GCP3Alp6, residues 499–503 (based on the predicted human GCP3 hinge region, 551–555; Guillet et al., 2011), is distal to the GCP3Alp6 N-terminal region (1–186), which interacts with Mzt1 (Figure 6F and Supplementary Figure S3). The N-terminal end of budding yeast GCP3Spc98 has been mapped to the base of the γ-TuSC (Choy et al., 2009). Considering the fact that purified recombinant Mzt1 forms oligomers, one possibility is that Mzt1 forms a multimer complex that fits deep inside the funnel-shaped γ-tubulin ring-like complex and adjusts the angle of the GCP3 (Figure 7). Narrowing down the Mzt1 interaction region in GCP3Alp6 and performing structural analysis of the Mzt1-Alp6 complex are essential to finding out the precise molecular mechanism by which Mzt1 regulates the γ-TuC.

Bottom Line: Mzt1/Tam4 depletion also causes cytokinesis defects, suggesting a role of the γ-tubulin complex in the regulation of cytokinesis.Yeast two-hybrid analysis shows that Mzt1/Tam4 forms a complex with Alp6, a fission yeast homologue of γ-tubulin complex protein 3 (GCP3).Together our results suggest that Mzt1/Tam4 contributes to the MTOC function through regulation of GCP3(Alp6).

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Leicester, Leicester LE1 9HN, United Kingdom Paterson Institute for Cancer Research, University of Manchester, Manchester M20 4BX, United Kingdom.

ABSTRACT
In humans, MOZART1 plays an essential role in mitotic spindle formation as a component of the γ-tubulin ring complex. We report that the fission yeast homologue of MOZART1, Mzt1/Tam4, is located at microtubule-organizing centers (MTOCs) and coimmunoprecipitates with γ-tubulin Gtb1 from cell extracts. We show that mzt1/tam4 is an essential gene in fission yeast, encoding a 64-amino acid peptide, depletion of which leads to aberrant microtubule structure, including malformed mitotic spindles and impaired interphase microtubule array. Mzt1/Tam4 depletion also causes cytokinesis defects, suggesting a role of the γ-tubulin complex in the regulation of cytokinesis. Yeast two-hybrid analysis shows that Mzt1/Tam4 forms a complex with Alp6, a fission yeast homologue of γ-tubulin complex protein 3 (GCP3). Biophysical methods demonstrate that there is a direct interaction between recombinant Mzt1/Tam4 and the N-terminal region of GCP3(Alp6). Together our results suggest that Mzt1/Tam4 contributes to the MTOC function through regulation of GCP3(Alp6).

Show MeSH