The University of Texas Medical School at Houston
Department of Microbiology and Molecular Genetics

Ziyin Li , Ph.D.

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  • Ziyin Li, Ph.D.Assistant Professor
  • Department of Microbiology &
    Molecular Genetics
  • University of Texas-Houston Medical School
    6431 Fannin Street, MSE R214
    Houston, Texas 77030
  • Telephone: (713) 500-5139
    Laboratory telephone: (713) 500-????
    e-mail: Ziyin.Li@uth.tmc.edu

 

Education:

Ph.D., Institute of Genetics, Chinese Academy of Sciences, 2000

Postdoctoral Fellow, University of California-San Francisco

Research Interests:

Cell cycle control and ubiquitin-dependent and -independent proteolytic pathways in the parasitic protozoan Trypanosoma brucei

We study the molecular and cellular mechanisms that control mitosis and cytokinesis in Trypanosoma brucei, a unicellular eukaryote and the causative agent of sleeping sickness in human. Compared with other eukaryotes, the cell division cycle of T. brucei possesses several unique features such as the coordination between the nuclear division cycle and the kinetoplast (mitochondrial DNA complex) division cycle, the lack of several key cell cycle checkpoints, and a unidirectional cleavage furrow ingression from the anterior toward the posterior of the cell without the involvement of the actomyosin contractile ring. The current focus is on the cell cycle regulatory circuits consisting of protein kinases, motor proteins, and ubiquitin ligases. In addition, we investigate the assembly, dynamics and function of the mitotic structures such as the mitotic spindle, kinetochores and the cleavage furrow. We use a combination of genetics, biochemistry, cell biology, and chemical genetics to elucidate the molecular and cellular basis of cell proliferation, which may provide novel targets for anti-trypanosomiasis chemotherapy.

We are also interested in the role of ubiquitin-dependent and -independent proteolysis in various cell biological processes. ATP-dependent protease complexes are present in all three kingdoms of life where they ride the cell of mis-folded or damaged proteins and control the level of certain regulatory proteins. These proteases include the 26S proteasome in eukaryotes, Archaea, and Actinomycetales and the HslVU protease in eubacteria. The co-existence of a 26S proteasome and an HslVU protease in one organism was previously considered unlikely, but both proteases are found in T. brucei, where the HslVU complex (TbHslVU) localizes to the single mitochondrion and its unique DNA complex, the kinetoplast DNA (kDNA), and regulates kDNA replication. TbHslVU is the first known regulator of kDNA replication. We are interested in investigating the function and regulation of various ubiquitin-dependent pathways and the HslVU-mediated proteolysis pathway in trypanosomes. The current focus is on three proteolytic pathways: the Cullin-RING ubiquitin ligase (CRL) and the anaphase-promoting complex/cyclosome (APC/C) on cell cycle control and HslVU protease on kDNA replication.

Lab Rotations: Available

The projects will be designed to investigate the unusual mechanisms of spindle assembly and cytokinesis as well as the regulation of diverse cellular processes by ubiquitin-dependent and -independent pathways by a combination of genetics (RNAi and gene knockout), biochemistry (protein purification, kinase assay, etc), cellular biology (immunofluorescence and electron microscopy, time-lapse video microscopy, etc), molecular biology and chemical genetic approaches.

Postdoctoral Position: Available

Self-motivated and career-oriented recent Ph.D. graduates with strong background in biochemistry, cell biology and molecular biology are encouraged to apply. Please submit a recent CV, a description of past achievements and future career goals along with the names and contact information of three references to Dr. Ziyin Li.

Selected Publications:

  • Li Z., Umeyama T., and Wang C.C. (2009) The Aurora kinase in Trypanosoma brucei plays distinctive roles in metaphase-anaphase transition and cytokinetic initiation. PLoS Pathog., (in press)
  • Li Z., Umeyama T., and Wang C.C. (2008) The chromosomal passenger complex and a mitotic kinesin interact with the Tousled-like kinase in trypanosomes to regulate mitosis and cytokinesis. PLoS ONE, 3(11): e3814 [abstract]
  • Li Z., and Wang C.C. (2008) KMP-11, a basal body and flagellar protein, is required for cell division in Trypanosoma brucei. Eukaryot. Cell, 7: 1941-1950 [abstract]
  • Li Z., Lee J.H., Chu F., Burlingame A.L., Günzl A., and Wang C.C. (2008) Identification of a novel chromosomal passenger complex and its unique localization during cytokinesis in Trypanosoma brucei. PLoS ONE, 3(6): e2354 [abstract]
  • Li Z., Lindsay M.E., Motyka S.A., Englund P.T., and Wang C.C. (2008) Identification of a bacterial-like HslVU protease in the mitochondria of Trypanosoma brucei and its role in mitochondrial DNA replication. PLoS Pathog., 4(4): e1000048 [abstract]
  • Li Z., Gourguechon S., and Wang C.C. (2007) Tousled-like kinase in a microbial eukaryote regulates spindle assembly and S-phase progression by interacting with Aurora kinase and chromatin assembly factors. J. Cell Sci., 120: 3883-3894 [abstract]
  • Li Z.*, Tu X.*, and Wang C.C. (2006) Okadaic acid overcomes the blocked cell cycle caused by depleting cdc2-related kinases in Trypanosoma brucei. Exp. Cell Res., 312: 3504-3516 (* equal contribution) [abstract]
  • Li Z., and Wang C.C. (2006) Changing roles of Aurora-B kinase in two life cycle stages of Trypanosoma brucei. Eukaryot. Cell, 5: 1026-1035 [abstract]
  • Tu X., Kumar P., Li Z., and Wang C.C. (2006) An Aurora kinase homologue is involved in regulating both mitosis and cytokinesis in Trypanosoma brucei. J. Biol. Chem., 281: 9677-9687 [abstract]
  • Li Y., Li Z., and Wang C.C. (2003) Differentiation of Trypanosoma brucei may be stage non-specific and does not require progression of cell cycle. Mol. Microbiol., 49: 251-265 [abstract]
  • Li Z., and Wang C.C. (2003) A PHO80-like cyclin and a B-type cyclin control the cell cycle of the procyclic form of Trypanosoma brucei. J. Biol. Chem., 278: 20652-20658 [abstract]
  • Li Z., and Wang C.C. (2002) Functional characterization of the 11 non-ATPase subunit proteins in the trypanosome 19S proteasomal regulatory complex. J. Biol. Chem., 277: 42686-42693 [abstract]
  • Li Z., Zou C.-B., Yao Y., Hoyt M.A., McDonough S., Mackey Z.B., Coffino P., and Wang C.C. (2002) An easily dissociated 26S proteasome catalyzes an essential ubiquitin-mediated protein degradation pathway in Trypanosoma brucei. J. Biol. Chem., 277: 15486-15498 [abstract]
[Search PubMed for more papers by Ziyin Li]