Bio

Honors & Awards


  • EMBO Prize, EMBO (05.2011)

Professional Education


  • Doctor of Philosophy, Ludwig Maximilian Universitat Munchen (2011)
  • Master of Science, Chinese Academy Of Sciences (2007)
  • Bachelor of Science, Unlisted University (2003)

Stanford Advisors


Research & Scholarship

Lab Affiliations


Publications

Journal Articles


  • The Cotranslational Function of Ribosome-Associated Hsp70 in Eukaryotic Protein Homeostasis CELL Willmund, F., del Alamo, M., Pechmann, S., Chen, T., Albanese, V., Dammer, E. B., Peng, J., Frydman, J. 2013; 152 (1-2): 196-209

    Abstract

    In eukaryotic cells a molecular chaperone network associates with translating ribosomes, assisting the maturation of emerging nascent polypeptides. Hsp70 is perhaps the major eukaryotic ribosome-associated chaperone and the first reported to bind cotranslationally to nascent chains. However, little is known about the underlying principles and function of this interaction. Here, we use a sensitive and global approach to define the cotranslational substrate specificity of the yeast Hsp70 SSB. We find that SSB binds to a subset of nascent polypeptides whose intrinsic properties and slow translation rates hinder efficient cotranslational folding. The SSB-ribosome cycle and substrate recognition is modulated by its ribosome-bound cochaperone, RAC. Deletion of SSB leads to widespread aggregation of newly synthesized polypeptides. Thus, cotranslationally acting Hsp70 meets the challenge of folding the eukaryotic proteome by stabilizing its longer, more slowly translated, and aggregation-prone nascent polypeptides.

    View details for DOI 10.1016/j.cell.2012.12.001

    View details for Web of Science ID 000313719800017

    View details for PubMedID 23332755

  • PolyQ Proteins Interfere with Nuclear Degradation of Cytosolic Proteins by Sequestering the Sis1p Chaperone. Cell Park, S. H., Kukushkin, Y., Gupta, R., Chen, T., Konagai, A., Hipp, M. S., Hayer-Hartl, M., Hartl, F. U. 2013; 154 (1): 134-45

    Abstract

    Dysfunction of protein quality control contributes to the cellular pathology of polyglutamine (polyQ) expansion diseases and other neurodegenerative disorders associated with aggregate deposition. Here we analyzed how polyQ aggregation interferes with the clearance of misfolded proteins by the ubiquitin-proteasome system (UPS). We show in a yeast model that polyQ-expanded proteins inhibit the UPS-mediated degradation of misfolded cytosolic carboxypeptidase Y(?) fused to green fluorescent protein (GFP) (CG(?)) without blocking ubiquitylation or proteasome function. Quantitative proteomic analysis reveals that the polyQ aggregates sequester the low-abundant and essential Hsp40 chaperone Sis1p. Overexpression of Sis1p restores CG(?) degradation. Surprisingly, we find that Sis1p, and its homolog DnaJB1 in mammalian cells, mediates the delivery of misfolded proteins into the nucleus for proteasomal degradation. Sis1p shuttles between cytosol and nucleus, and its cellular level limits the capacity of this quality control pathway. Upon depletion of Sis1p by polyQ aggregation, misfolded proteins are barred from entering the nucleus and form cytoplasmic inclusions.

    View details for PubMedID 23791384

  • DnaK Functions as a Central Hub in the E. coli Chaperone Network Cell Reports Taotao Chen, G., Sonya M. Schermann, Hung-chun Chang, Pierre Genevaux, Federico Agostini, Gian Gaetano Tartaglia, Manajit Hayer-Hartl, F. Ulrich Hartl 2012; 1 (3): 251-264
  • Proteomics identification of differentially expressed proteins associated with pollen germination and tube growth reveals characteristics of germinated Oryza sativa pollen MOLECULAR & CELLULAR PROTEOMICS Dai, S., Chen, T., Chong, K., Xue, Y., Liu, S., Wang, T. 2007; 6 (2): 207-230

    Abstract

    Mature pollen from most plant species is metabolically quiescent; however, after pollination, it germinates quickly and gives rise to a pollen tube to transport sperms into the embryo sac. Because methods for collecting a large amount of in vitro germinated pollen grains for transcriptomics and proteomics studies from model plants of Arabidopsis and rice are not available, molecular information about the germination developmental process is lacking. Here we describe a method for obtaining a large quantity of in vitro germinating rice pollen for proteomics study. Two-dimensional electrophoresis of approximately 2300 protein spots revealed 186 that were differentially expressed in mature and germinated pollen. Most showed a changed level of expression, and only 66 appeared to be specific to developmental stages. Furthermore 160 differentially expressed protein spots were identified on mass spectrometry to match 120 diverse protein species. These proteins involve different cellular and metabolic processes with obvious functional skew toward wall metabolism, protein synthesis and degradation, cytoskeleton dynamics, and carbohydrate/energy metabolism. Wall metabolism-related proteins are prominently featured in the differentially expressed proteins and the pollen proteome as compared with rice sporophytic proteomes. Our study also revealed multiple isoforms and differential expression patterns between isoforms of a protein. These results provide novel insights into pollen function specialization.

    View details for DOI 10.1074/mcp.M600146-MCP200

    View details for Web of Science ID 000244414900003

    View details for PubMedID 17132620

  • Proteomic analyses of Oryza sativa mature pollen reveal novel proteins associated with pollen germination and tube growth PROTEOMICS Dai, S., Li, L., Chen, T., Chong, K., Xue, Y., Wang, T. 2006; 6 (8): 2504-2529

    Abstract

    As a highly reduced organism, pollen performs specialized functions to generate and carry sperm into the ovule by its polarily growing pollen tube. Yet the molecular genetic basis of these functions is poorly understood. Here, we identified 322 unique proteins, most of which were not reported previously to be in pollen, from mature pollen of Oryza sativa L. ssp japonica using a proteomic approach, 23% of them having more than one isoform. Functional classification reveals that an overrepresentation of the proteins was related to signal transduction (10%), wall remodeling and metabolism (11%), and protein synthesis, assembly and degradation (14%), as well as carbohydrate and energy metabolism (25%). Further, 11% of the identified proteins are functionally unknown and do not contain any conserved domain associated with known activities. These analyses also identified 5 novel proteins by de novo sequencing and revealed several important proteins, mainly involved in signal transduction (such as protein kinases, receptor kinase-interacting proteins, guanosine 5'-diphosphate dissociation inhibitors, C2 domain-containing proteins, cyclophilins), protein synthesis, assembly and degradation (such as prohibitin, mitochondrial processing peptidase, putative UFD1, AAA+ ATPase), and wall remodeling and metabolism (such as reversibly glycosylated polypeptides, cellulose synthase-like OsCsLF7). The study is the first close investigation, to our knowledge, of protein complement in mature pollen, and presents useful molecular information at the protein level to further understand the mechanisms underlying pollen germination and tube growth.

    View details for DOI 10.1002/pmic.200401351

    View details for Web of Science ID 000237398700019

    View details for PubMedID 16548068

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