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Functional Analysis of the Tubulin-Folding Cofactor C in Arabidopsis thaliana

2002; Elsevier BV; Volume: 12; Issue: 17 Linguagem: Inglês

10.1016/s0960-9822(02)01109-0

1879-0445

Victor Kirik, Jaideep Mathur, Paul E. Grini, Irene Klinkhammer, Klaus Adler, Nicole Bechtold, Michel Herzog, Jean‐Marc Bonneville, Martin Hülskamp,

DNA Repair Mechanisms

The biogenesis of microtubules comprises several steps, including the correct folding of α- and β-tubulin and heterodimer formation. In vitro studies and the genetic analysis in yeast revealed that, after translation, α- and β-tubulin are processed by several chaperonins [1Rommelaere H. Troys M.V. Gao Y. Meli R. Cowan N.J. Vandekerckhove J. Ampe C. The eukaryotic cytosolic chaperonin contains t-complex polypeptide 1 and seven related subunits.Proc. Natl. Acad. Sci. USA. 1993; 90: 11975-11979Crossref PubMed Scopus (116) Google Scholar, 2Kubota H. Hynes G. Carne A. Ashworth A. Willison K. Identification of six Tcp-1-related genes encoding divergent subunits of the TCP-1-containing chaperonin.Curr. Biol. 1994; 4: 89-99Abstract Full Text Full Text PDF PubMed Scopus (272) Google Scholar] and microtubule-folding cofactors (TFCs) to produce assembly-competent α-/β-tubulin heterodimers [3Gao Y. Meli R. Walden P.D. Lewis S.A. Ampe C. Rommelaere H. Vandekerckhove J. Cowen N.J. A novel cochaperonin that modulates the ATPase activity of cytoplasmic chaperonin.J. Cell Biol. 1994; 125: 989-996Crossref PubMed Scopus (75) Google Scholar, 4Tian G. Huang Y. Rommelaere H. Vanddekerckhove J. Ampe C. Cowan N.J. Pathway leading to correctly folded β-tubulin.Cell. 1996; 86: 287-296Abstract Full Text Full Text PDF PubMed Scopus (239) Google Scholar, 5Melki R. Rommelaere H. Leguy R. Vandekerckhove J. Ampe C. Cofactor A is a molecular chaperone required for β-tubulin folding functional and structural characterization.Biochemistry. 1996; 35: 10422-10435Crossref PubMed Scopus (57) Google Scholar, 6Lewis S.A. Tian G. Cowan N.J. The α- and β-tubulin folding pathways.Trends Cell Biol. 1997; 7: 479-484Abstract Full Text PDF PubMed Scopus (131) Google Scholar, 7Llosa M. Aloria K. Campo R. Padilla R. Avila J. Sanchez-Pulido L. Zabala J.C. The β-tubulin monomer release factor (p14) has homology with a region of the DnaJ protein.FEBS Lett. 1996; 397: 283-289Abstract Full Text PDF PubMed Scopus (29) Google Scholar, 8Archer J.E. Vega L.R. Solomon F. Rbl2p, a yeast protein that binds to β-tubulin and participates in microtubule function in vivo.Cell. 1995; 82: 425-434Abstract Full Text PDF PubMed Scopus (75) Google Scholar, 9Hirata D. Masuda H. Eddison M. Toda T. Essential role of tubulin-folding cofactor D in microtubule assembly and its association with microtubules in fission yeast.EMBO J. 1998; 17: 658-666Crossref PubMed Scopus (72) Google Scholar, 10Radcliffe P.A. Garcia M.A. Toda T. The cofactor-dependent pathways for α- and β-tubulins in microtubule biogenesis are functionally different in fission yeast.Genetics. 2000; 156: 93-103PubMed Google Scholar, 11Radcliffe P.A. Hirata D. Vardy L. Toda T. Functional dissection and hierarchy of tubulin-folding cofactor homologues in fission yeast.Mol. Biol. Cell. 1999; 10: 2987-3001Crossref PubMed Scopus (66) Google Scholar]. One of the TFCs, TFC-C, does not exist in yeast, and a potential function of TFC-C is thus based only on the biochemical analysis. In this study and in a very recently published study by Steinborn and coworkers [12Steinborn K. Maulbetsch C. Priester B. Trautmann S. Pacher T. Geiges B. Kuttner F. Lepiniec L. Stierhof Y.-D. Schwarz H. et al.The Arabidopsis PILZ group genes encode tubulin-folding cofactor orthologs required for cell division but not cell growth.Genes Dev. 2002; 16: 959-971Crossref PubMed Scopus (130) Google Scholar], the analysis of the Arabidopsis porcino (por) mutant has shown that TFC-C is important for microtubule function in vivo. The predicted POR protein shares weak amino acid similarity with the human TFC-C (hTFC-C). Our finding that hTFC-C under the control of the ubiquitously expressed 35S promoter can rescue the por mutant phenotype shows that the POR gene encodes the Arabidopsis ortholog of hTFC-C. The analysis of plants carrying a GFP:POR fusion construct showed that POR protein is localized in the cytoplasm and is not associated with microtubules. While, in por mutants, microtubule density was indistinguishable from wild-type, their organization was affected.