Ruprecht-Karls-Universität Heidelberg
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Melchior0118 - Scientist (f/m) / PhD position
Project no:

Project leader:

Project supervisor:
Melchior, Frauke
Application deadline:
15. Mar 2018
Start of PhD project:
1. Apr 2018

Project description:

SUMO as regulator of nuclear import
Reversible protein SUMOylation is an essential process that regulates hundreds of individual proteins in numerous pathways including nucleocytoplasmic transport. Nuclear transport factors such as the GTPase Ran, the GTPase activating protein RanGAP1 and transport receptors of the importin beta family are subject to SUMOylation. Moreover, we recently discovered that some mammalian and yeast transport receptors can bind SUMO non-covalently, making them ideal candidates for regulated nuclear import of SUMOylated proteins in response to different stimuli.
The PhD student project aims to gain insights into the role of the SUMO interaction motif in selected nuclear transport receptors. One line of investigation will involve mass spectrometry based identification of SUMO-dependent cargoes of these nuclear import receptors. Interesting candidates will be examined in vitro (e.g. by in vitro SUMOylation and nuclear import assays) and in cellulo (e.g. by SUMO immunoprecipitation and fluorescence microscopy) to uncover molecular details and functional consequences of SUMOylation-triggered nuclear entry. To gain structural insights into the molecular details of these interactions, a collaboration with a Structural Biology group has been initiated. A second line of investigation will focus on the cellular role of the SUMO interaction motif in these nuclear import receptors. Upon creation of mammalian cell lines lacking the SUMO interaction motif using CRISPR/Cas9 techniques, we will assess the effect on transport receptor and cargo localization, stability and interactions of the transport receptor as well as cellular consequences by immunofluorescence, IP/mass spectrometry and diverse cell-based assays.
Flotho, F. and Melchior, F. (2013) SUMOylation - a regulatory protein modification in health and disease. Annu. Rev. Biochem. 82, 357-385.

Becker, J., Barysch, S.V., Karaca, S., Hsiao, H.H., Berriel Diaz, M., Herzig, S., Urlaub, S., Melchior, F. (2013) Endogenous SUMOylation: Detection of targets in mammalian cells and tissues. Nat. Struct. & Mol. Biol. 20, 525-31.

Sakin, V., Richter, S.M., Hsiao, H.-H., Urlaub, H. and Melchior, F. (2015) Sumoylation of the GTPase Ran by the RanBP2 SUMO E3 Ligase Complex. Journal of Biological Chemistry 290, 23589–23602

Ritterhoff, T., Das, H., Hofhaus, G., Schröder, R.R., Flotho, A. and Melchior, F. (2016) The RanBP2/RanGAP1*SUMO1/Ubc9 SUMO E3 ligase is a disassembly machine for Crm1-dependent nuclear export complexes. Nat. Commun. 7, 11482, doi: 10.1038/ncomms11482
Methods that will be used:
A wide range of biochemical, molecular biological and cell biological methods including protein expression, purification and crystallization, pull downs, in vitro SUMOylation, in vitro nuclear import assays, mammalian cell culture including gene editing by the CRISPR/Cas9 technique, plasmid transfection, immunoprecipitation, immunofluorescence and others.
Cooperation partners:
We are seeking a highly motivated PhD student with a strong background in protein biochemistry and cell biology and a broad interest in fundamental aspects of cellular functions. The successful candidate will be part of a very collaborative and international team of Postdocs, PhD students, Master students and technicians.
Personal qualifications: