Yixian Zheng

Staff Member


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(410) 246-3032
(410) 246-3020
(410) 243-6311
Yixian Zheng

RESEARCH INTERESTS

Microtubule Nucleation and Organization During the Cell Cycle

How a cell organizes its interior and divides are central questions in cell and developmental biology. Research in my lab focuses on understanding how the cell nucleates and organizes microtubules to achieve intracellular organization and cell division.

The major microtubule nucleation site inside an animal cell is the centrosome. One research avenue in my lab is to understand the structure and function of the centrosome using Xenopus, Drosophila, and mammalian tissue culture cells. The centrosome consists of a pair of centrioles and an electron-dense pericentriolar material (PCM) which harbors the activity for microtubule nucleation and organization. We discovered a γ-Tubulin containing Ring Complex (γTuRC) and showed that it can nucleate microtubules in vitro. Furthermore, we found, that γTuRC is essential for centrosomes to nucleate microtubules. Our current hypothesis is that the γTuRC is the major microtubule nucleator at the PCM. γTuRC consists of approximately 6 presently uncharacterized proteins in addition to γ-tubulin. We are using a combination of molecular genetic, biochemical and genetic approaches to understand this ring complex. We are particularly interested in addressing how the γTuRC is involved in regulating microtubule nucleating activity of the centrosome, how it is recruited to and assembled at the PCM and whether and how it is involved in centrosome duplication.

In animal cells, the transition from interphase to mitosis is accompanied by dramatic changes in cellular architecture such as nuclear envelope break down, chromosome condensation and spindle formation. Another direction in my lab is to understand the signals that regulate spindle assembly during mitosis. The reorganization of the interphase microtubule array into a highly dynamic mitotic spindle requires more than the presence of centrosomes and the conversion of cytosol into a mitotic state. Several studies have shown that nuclear signals released into the cytoplasm upon nuclear envelope breakdown exert many different effects on microtubule arrays. Recently, we discovered that the nuclear GTPase, Ran, can stimulate microtubule aster and spindle formation in the absence of both centrosomes and chromosomes. Our findings suggest that Ran is the nuclear signal that regulates microtubule assembly in mitosis.

Recently we found that a carboxyl-terminal region of the nuclear mitotic apparatus protein (NuMA), a nuclear protein required for organizing mitotic spindle poles, mimics Ran’s ability to induce microtubule asters. This NuMA fragment also specifically interacted with the nuclear transport factor, importin-β, a receptor for protein import into the nucleus. Importin-β is an inhibitor of microbutule assembly in Xenopus egg extracts, and Ran regulates the interaction between importin-β and NuMA. Importin-β therefore links NuMa to regulation by Ran. This suggests that similar mechanisms regulate nuclear import during interphase and spindle assembly during mitosis.

Considering the complexity of spindle assembly, other mitotic microtubule regulators are likely to be regulated by Ran through importin-β. Indeed, several characterized microtubule regulators were found to be nuclear in interphase, suggesting an interaction with the nuclear import pathway. Based on our findings, we hypothesize that Ran may regulate the activity of these proteins in mitosis via importin-β. The next challenge is to understand the mechanism of importin-β-mediated regulation of spindle assembly.


PUBLICATIONS

1. Zheng Y, Jung MK, and Oakley BR (1991). gamma-tubulin is present in Drosophila melanogaster and Homo sapiens and is associated with the centrosome. Cell 65, 817-823.

2. Zheng Y, Wong ML, Alberts B, and Mitchison TJ (1995). A gamma-tubulin ring complex from the unfertilized egg of Xenopus laevis can nucleate microtubule assembly in vitro. Nature 378, 578-583. (Research Article; News and Views: Oakley, Nature 378, 555-556)

3. Wilson PG, Zheng Y, Oakley CE, Oakley BR, Borisy GG, and Fuller MT (1997). Differential expression of two gamma-tubulin isoforms during gametogenesis and development in Drosophila. Developmental Biology 184, 207-221.

4. Dictenberg JB, Zimmerman W, Sparks CA, Young A, Vidair C, Zheng Y, Carrington W, Fay FS, Doxsey SJ (1998). Pericentrin and Gamma-Tubulin Form a Protein Complex and Are Organized into A Novel Lattice at the Centrosome. Journal Cell Biology 141, 163-174.

5. Martin O, Gunawardane R., Iwamatsu A, and Zheng Y (1998). Xgrip109: A gamma-tubulin associated protein with an essential role in βTuRC assembly and centrosome function. Journal of Cell Biology 141, 675-687.

6. Moritz M, Zheng Y, Alberts B, and Oegema K (1998). Recruitment of the gamma-tubulin ring complex to Drosophila salt-stripped centrosome scaffolds. Journal of Cell Biology 142, 775-786.

7. Zheng Y, Wong ML, Alberts B, and Mitchison T (1998). Purification and assay of gamma-tubulin ring complex. Methods in Enzymology 298, Part B, 218-228.

8. Field CM, Oegema K., Zheng Y, Mitchison T, and Walczak CE (1998). Purification of Cytoskeletal Proteins Using Peptide Antibodies. Methods in Enzymology 298, Part B, 525-541.

9. Oegema K, Wiese C, Martin OC, Milligan RA, Iwamatsu A, Mitchison T, and Zheng Y (1999). Characterization of Two Related Drosophila gamma-tubulin Complexes that Differ in Their Ability to Nucleate Microtubules. Journal of Cell Biology 144, 721-733.

10. Wiese C and Zheng Y (1999). Gamma-Tubulin Complexes and Their Interaction with Microtubule Organizing Centers. Current Opinion in Structural Biology 9, 250-259.

11. Wilde A and Zheng Y (1999). Stimulation of Microtubule Aster Formation and Spindle Assembly in Xenopus Egg Extracts by the Small GTPase Ran. Science 284, 1359-1362. (News Focus: Pennisi, Science 284, 1260-1261, 1999; Commentary: Desai and Hyman, Current Biology 9, R704-707, 1999).

12. Wiese C and Zheng Y (2000). A New Function for the Gamma-tubulin Ring Complex as a Microtubule Minus-end Cap. Nature Cell Biology 2, 358-364. (News and Views: Erickson, Nature Cell Biology 2, E93-E96).

13. Zhang L, Keating T, Wilde, A, Borisy G, and Zheng Y (2000). The Role of Xgrip210 in Gamma-Tubulin Ring Complex Assembly and Centrosome Recruitment. Journal of Cell Biology 151, 1525–1535.

14. Gunawardane R, Martin O, Cao K, Zhang L, Dej K, Iwamatsu A, and Zheng Y (2000). Characterization and Reconstitution of Drosophila Gamma-Tubulin Ring Complex Subunits. Journal of Cell Biology 151, 1513–1523.

15. Gunawardane R, Lizarraga S, Wiese C, Wilde A, and Zheng Y (2000). Gamma-Tubulin Complexes and Their Role in Microtubule Nucleation. In The Centrosome in Cell Replication and Early Development. pp 55-73. Academic Press (Book).

16. Gunawardane RN, Lizarraga SB, Wiese C, Wilde A, and Zheng Y (2000). Gamma-Tubulin Complexes and Their Role in Microtubule Nucleation. Current Topics in Developmental Biology 49, 55-73.

17. Wilde A, Lizarraga S, Zhang L, Wiese C, Gliksman N, Walczak C, and Zheng Y (2001). Ran stimulates spindle assembly by changing microtubule dynamics and the balance of motor activities. Nature Cell Biology 3, 221-227. (News and Views: Walczak, Nature Cell Biology 3, E69-70, 2001).

18. Wiese C, Wilde A, Adam S, Moore M, Merdes A, and Zheng Y (2001). Role of Importin-beta in Coupling Ran to Downstream Targets in Microtubule Assembly. Science 291, 653-656. (News and Views: Walczak, Nature Cell Biology 3, E69-70, 2001).

19. Gunawardane RN, Zheng Y, Oegema K, Wiese C (2001). Purification and reconstitution of Drosophila gamma-tubulin complexes. Methods in Cell Biology 67, 1-25.

20. Lizarraga SB, Zheng Y, Wilde AR (2002). Characterization of the effects of RanGTP on the microtubule cytoskeleton. Methods in Molecular Biology 189, 247-260.

21. Gunawardane R, Martin OC, and Zheng Y (2003). Characterization of a new gammaTuRC subunit with WD repeats. Molecular Biology of the Cell 14, 1017-1026.

22. Tsai MY, Wiese C, Cao K, Martin OC, Donovan P, Ruderman J, Prigent C, and Zheng Y (2003). A Ran-signaling pathway mediated by the mitotic kinase Aurora A in spindle assembly. Nature Cell Biology 5, 242-248.

23. Li HY, Wirtz D, and Zheng Y (2003). A mechanism of coupling RCC1 mobility to RanGTP production on the chromatin in vivo. Journal of Cell Biology 160, 635-644.

24. Li HY, Cao K, and Zheng Y. (2003) Ran in spindle checkpoint: a new function for a versatile GTPase. Trends in Cell Biology 13, 553-557.

25. Cao K, Nakajima R, Meyer HH, and Zheng Y. (2003). The AAA-ATPase Cdc48/p97 regulates spindle disassembly at the end of mitosis. Cell 115, 355-367. (Highlight: Nature Reviews Molecular Cell Biology 4, 906, 2003; Commentary: Cheeseman and Desai, Current Biology 14, R70-72, 2004).

26. Ems-McClung SC, Zheng Y, Walczak CE (2004). Importin α/β and Ran-GTP Regulate XCTK2 Microtubule Binding through a Bipartite Nuclear Localization Signal. Molecular Biology of the Cell 15, 46-57.

27. Kawaguchi S and Zheng Y (2004). Characterization of a Drosophila Centrosome Protein CP309 That Shares Homology with Kendrin and CG-NAP. Molecular Biology of the Cell 15, 37-45.

28. Li HY and Zheng Y (2004). Mitotic phosphorylation of RCC1 is essential for RanGTP gradient production and spindle assembly in mammalian cells. Genes and Development 18, 512-527.

29. Cao K and Zheng Y (2004). The Cdc48/p97-Ufd1-Npl4 Complex: Its Potential Role in Coordinating Cellular Morphogenesis during the M-G1 Transition. Cell Cycle 3, 422-424.

30. Li HY and Zheng Y (2004). The Production and Localization of GTP-Bound Ran in Mitotic Mammalian Tissue Culture Cells. Cell Cycle 3, 993-995.

31. Ducat DC and Zheng Y (2004). Aurora kinases in spindle assembly and chromosome segregation. Experimental Cell Research 301, 60-67.

32. Nakajima, R, Tsai, M-Y, and Zheng Y (2004). Centrosomes and Microtubule Nucleation, Encyclopedia of Biological Chemistry 1, 372-376. W. J. Lennarz and M. D. Lane (Ed), Elsevier Inc.

33. Zheng Y (2004). G Protein Control of Microtubule Assembly, Annual Review of Cell and Developmental Biology 20, 867-894.

34. Tsai, M-Y and Zheng Y (2005). Aurora A Kinase-Coated Beads Function as Microtubule-Organizing Centers and Enhance RanGTP-Induced Spindle Assembly. Current Biology 15, 2156-2163.

35. Vong, QP, Cao K, Li HY, Iglesias PA, and Zheng Y (2005). Chromosome Alignment and Segregation Regulated by Ubiquitination of Survivin. Science 310, 1499-1504. (Perspective: Earnshaw, Science 310, 1443-1444).

36. Tsai M-Y, Wang S, Heidinger JM, Shumaker D, Adam SA, Goldman RD, and Zheng Y (2006). A Mitotic Lamin B Matrix Induced by RanGTP Required for Spindle Assembly. Science 311, 1887-1893. (Research Article; News and Views: Hayes, Nature Cell Biology 8, p550, 2006; Research Highlight: Nature Reviews Molecular Cell Biology 7, p307, 2006).

37. Goodman B and Zheng Y (2006). Mitotic spindle morphogenesis: Ran on the microtubule cytoskeleton and beyond. Biochemical Society Transactions 34, 716-721.

38. Wiese C and Zheng Y (2006). Microtubule nucleation: gamma-tubulin and beyond. Journal of Cell Science 119, 4143-4153.

39. Zheng Y and Tsai M-Y (2006). The Mitotic Spindle Matrix: A Fibro-Membranous Lamin Connection. Cell Cycle 5, 2345-2347.

40. Spradling AC and Zheng Y (2007). The Mother of All Stem Cells? Science 315, 469-470.


LAB MEMBERS

Josh Bembenek, P/D Fellow (HHMI)
Rong Chen, Technician (HHMI)
Ben Goodman, Predoc Fellow
Junling Jia, P/D Fellow (HHMI)
Youngjo Kim, P/D Fellow (HHMI)
Zhonghua Liu, P/D Fellow (HHMI)
Alexis Lomakin, P/D Fellow
Ona Martin, Technician (HHMI)
Katie McDole, Predoc Fellow
Changji Shi, Predoc Fellow
Anna Talaga, Rotation Student
Shusheng Wang, Research Associate
Junqi Zhang, Visiting Scientist