School of Humanities and Sciences


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  • Rahul Samant

    Rahul Samant

    Basic Life Science Research Associate, Biology
    Postdoctoral Research Fellow, Biology

    Current Research and Scholarly InterestsProtein misfolding in the cell creates toxic species linked to an array of diseases. Protective cellular protein quality control (PQC) mechanisms evolved to selectively recognize misfolded proteins and limit their toxic effects. Molecular chaperones recognize misfolded proteins, while the ubiquitin-proteasome system (UPS) promotes their clearance through the attachment of ubiquitin chains. We previously identified a PQC pathway for spatial sequestration and clearance of misfolded proteins, conserved from yeast to humans, that is amplified when the UPS is impaired. However, the identity of the E3 ubiquitin ligases involved in this pathway—and how they interact with the chaperone machinery—is unresolved. Starting with a fluorescence microscopy-based genetic screen in yeast, we show that distinct chaperone and ubiquitination circuitries cooperate in PQC of soluble misfolded proteins in the cytoplasm and nucleus. In contrast with the canonical model where Lys48-linked ubiquitin chains are sufficient for proteasomal targeting, we found that cytoplasmic misfolded proteins requires tagging with mixed ubiquitin chains that contain both Lys11 and Lys48 linkages to be degraded. Each type of linkage-specific ubiquitination requires a distinct combination of ubiquitin ligases and chaperones. Strikingly, unlike cytoplasmic PQC, proteasomal degradation of nuclear misfolded proteins only requires Lys48 ubiquitin linkages and is independent of Lys11-specific circuits. We conclude that cytoplasmic and nuclear PQC involve combinatorial recognition by defined sets of cooperating systems. The distinct PQC requirements reveal underlying differences in nuclear and cytoplasmic proteome management, with important implications for our understanding of a wide range of diseases.

  • Feroza Sanjana

    Feroza Sanjana

    Graduate Visiting Researcher Student, Political Science

    BioFeroza Sanjana is a recipient of the Stanford Free University Graduate Fellowship 2018 and visiting doctoral researcher at the Department of Political Science. She is a PhD candidate and Thyssen Fellow at the Berlin Graduate School for Transnational Studies, a joint programme of Free University, Hertie School of Governance and the Wissenschaftszentrum Berlin für Sozialforschung (WZB) in Berlin. Her research interests lie in the international political economy of the Global South, in particular the diffusion of bilateral investment treaties. She has a Masters degree from London School of Economics (LSE).

  • Johannes Daniel Scharwies

    Johannes Daniel Scharwies

    Postdoctoral Research Fellow, Biology

    BioJohannes received his BSc from the Leibniz Universität Hannover (Germany) in Plant Biotechnology in the Fruit Science laboratory of Prof. Moritz Knoche. Inspired by research on water relations of fruit in the Knoche laboratory, Johannes joined the group of Prof. Stephen Tyerman at The University of Adelaide (Australia) with funding through the German Academic Exchange Service. Initially, his work focused on hydraulic properties of grape clusters for which he received his MSc in Agricultural Science. Afterwards, he joined the ARC Centre of Excellence in Plant Energy Biology through the Tyerman laboratory and specialised in molecular plant physiology by studying the role of aquaporins in plant responses to drought for a PhD. He investigated aquaporins, which are molecular channels in plant membranes that provide a gating mechanism for water fluxes and other small molecules, through a combination of gene expression analysis and utilization of transgenic overexpression and CRISPR-Cas9 knockout lines. His work was funded by the highly competitive Adelaide Scholarship International and a Supplementary Scholarship provided by the ARC Centre of Excellence in Plant Energy Biology. In April 2018, Johannes joins the laboratory of Assoc. Prof. José Dinneny at Stanford University as a Postdoctoral Scholar.

    Johannes research focuses on plant hydraulics from a molecular scale up to whole plants. He is interested on how plants perceive and adapt to changes in the environment in particular related to water. This ranges from developmental decisions to molecular control of water movement, for example through aquaporins. In José Dinneny's lab, he will continue work on hydropatterning, a phenomenon investigated in this laboratory previously.